AP Chemistry Flashcards: Complete 9-Unit Course Review
Review all nine AP Chemistry units with 450 cards covering concepts, models, equations, calculation setup, and laboratory reasoning.
เกี่ยวกับเด็คนี้
Review AP® Chemistry through 450 independently written English flashcards arranged in the course's nine-unit sequence. The deck moves from atomic structure and compound structure through properties of substances and mixtures, reactions, kinetics, thermochemistry, equilibrium, acids and bases, and thermodynamics and electrochemistry. Prerequisites come before dependent models and calculations.
What the cards practice
The cards use five recall paths: concept to explanation; model or representation to interpretation; equation to meaning and use; short setup to a result with units and reasoning; and laboratory observation to a chemical conclusion. They cover definitions, relationships, conditions, contrasts, particle and energy models, focused calculation steps, measurements, errors, and visible changes.
Selected reverse and contrast prompts appear only when the reverse direction has one clear standalone target. The deck excludes mechanical permutations, graph-dependent prompts that require a missing figure, copied test formats, long multipart derivations, and visual recall tied to third-party figures. The review scheduler handles long-term spacing after installation.
See the official AP Chemistry course page for College Board's current course requirements.
The Common knowledge · CC0 1.0 label applies only to the independently written prompts, answers, examples, organization, metadata, and inherited original cover, to the extent applicable rights exist. It does not claim ownership of scientific facts or equations.
This is an independent, unofficial study aid. It is not affiliated with, endorsed by, sponsored by, or official material from College Board or the AP Program. AP® is a trademark registered by the College Board, which is not affiliated with, and does not endorse, this product. No College Board examination questions, answer choices, scoring materials, curriculum text, logos, or trade dress were copied.
การ์ดในเด็คนี้
การ์ด 1
คำถาม
What does one mole count?
คำตอบ
Exactly 6.02214076 × 10^23 representative particles.
การ์ด 2
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What does a peak in an element's mass spectrum represent?
คำตอบ
An isotope with a particular mass-to-charge ratio; for singly charged monatomic ions, the position tracks isotopic mass.
การ์ด 3
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What does an empirical formula show?
คำตอบ
The lowest whole-number ratio of the elements' atoms in a compound.
การ์ด 4
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How does a mixture differ from a pure substance at the particle level?
คำตอบ
A mixture contains chemically distinct representative units in variable proportions; a pure substance contains one element or compound with fixed composition. Different isotopes do not make an elemental sample a mixture.
การ์ด 5
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Which particles make up an atom's nucleus?
คำตอบ
Protons and neutrons. Electrons occupy the space outside the nucleus.
การ์ด 6
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What does a larger binding energy on a PES spectrum mean?
คำตอบ
More energy is required to remove that electron, so it is held more strongly by the nucleus.
การ์ด 7
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How does atomic radius generally change across a period and down a group?
คำตอบ
It decreases from left to right as effective nuclear charge rises, and it increases down a group as additional electron shells increase distance and shielding.
การ์ด 8
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What typical ion charge do Group 1 metals form?
คำตอบ
+1, by losing their one valence electron.
การ์ด 9
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How do you convert moles to particles?
คำตอบ
Multiply by Avogadro's number: particles = moles × 6.022 × 10^23 mol^-1.
การ์ด 10
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How is average atomic mass estimated from isotope data?
คำตอบ
Add each isotopic mass multiplied by its fractional abundance.
การ์ด 11
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How is an element's mass percent in a compound calculated?
คำตอบ
Divide the mass contributed by that element by the compound's molar mass, then multiply by 100%.
การ์ด 12
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How can measured elemental composition reveal a sample's purity?
คำตอบ
Compare the measured mass fraction with the fraction expected for the pure compound; a mismatch indicates another component.
การ์ด 13
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How do you build a ground-state electron configuration with the Aufbau principle?
คำตอบ
For ordinary ground states, move through the periodic table in atomic-number order, filling each s, p, d, or f block as it appears. The subshell capacities are s², p⁶, d¹⁰, and f¹⁴. For example, Br is [Ar] 4s² 3d¹⁰ 4p⁵.
การ์ด 14
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What does the relative area or height of an ideal PES peak indicate?
คำตอบ
The relative number of electrons in the corresponding subshell.
การ์ด 15
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How does first ionization energy generally change across a period and down a group?
คำตอบ
It increases from left to right as effective nuclear charge rises, and it decreases down a group as distance and shielding make a valence electron easier to remove.
การ์ด 16
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Why do elements in the same group form similar compounds?
คำตอบ
Their ground-state valence patterns repeat, including which outer subshells are full or partly full. That leads to similar bonding and typical ion charges.
การ์ด 17
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How do you convert a sample's mass to moles?
คำตอบ
Divide its mass by its molar mass: n = m/M.
การ์ด 18
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Which mass-spectrum interpretation lies outside the usual single-element model used in this deck?
คำตอบ
Assigning peaks in mixtures or peaks from multiply charged or polyatomic species; the standard model uses singly charged monatomic ions of one element.
การ์ด 19
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What does the law of definite proportions state?
คำตอบ
Every pure sample of a given compound has the same element mass ratios.
การ์ด 20
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Why can two samples of the same mixture have different compositions?
คำตอบ
Mixture components are physically combined, so their relative amounts are not fixed by a chemical formula.
การ์ด 21
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How does Coulomb's law connect charge and separation to attraction?
คำตอบ
Attraction grows with the magnitude of the charge product and decreases with the square of the separation distance.
การ์ด 22
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Which PES electrons usually appear at the highest binding energy?
คำตอบ
Core electrons closest to the nucleus, because they feel the strongest nuclear attraction.
การ์ด 23
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How does electron affinity generally change across a period and down a group?
คำตอบ
Electron gain generally becomes more favorable from left to right across a period and less favorable down a group as distance and shielding increase. Stable subshell patterns create substantial exceptions.
การ์ด 24
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Why are alkali metals generally more reactive down the group?
คำตอบ
Their valence electron is farther from the nucleus and easier to remove.
การ์ด 25
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How many moles are in 18.0 g of H₂O?
คำตอบ
About 0.999 mol. Use 18.0 g ÷ 18.02 g mol^-1.
การ์ด 26
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An element is 75% isotope 10 and 25% isotope 11; what is its average atomic mass?
คำตอบ
10.25 u. Calculate (0.75 × 10) + (0.25 × 11).
การ์ด 27
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A compound is 40.0% C, 6.7% H, and 53.3% O by mass; what is its empirical formula?
คำตอบ
CH₂O. For a 100 g sample, convert each mass to moles and divide by the smallest amount.
การ์ด 28
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A 10.0 g impure sample contains 8.5 g of the target compound; what is its mass-percent purity?
คำตอบ
85%. Calculate (8.5 g ÷ 10.0 g) × 100%.
การ์ด 29
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Which electrons are removed first when a transition metal forms a cation?
คำตอบ
Electrons in the occupied orbital with the highest principal quantum number: 4s before 3d. For example, Fe²⁺ is [Ar] 3d⁶.
การ์ด 30
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A PES spectrum has peaks proportional to 2, 2, and 6 electrons; which configuration fits?
คำตอบ
1s² 2s² 2p⁶, the configuration of Ne.
การ์ด 31
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How does electronegativity generally change across a period and down a group?
คำตอบ
It increases from left to right across a period and decreases down a group as atomic size and shielding increase.
การ์ด 32
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What empirical formula results from Al³⁺ and O²⁻?
คำตอบ
Al₂O₃, because two Al³⁺ ions balance three O²⁻ ions.
การ์ด 33
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How does a particle's mass in atomic mass units relate to its molar mass?
คำตอบ
The numerical value is the same: a molecular or formula-unit mass of x u corresponds to a molar mass of x g mol^-1.
การ์ด 34
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What does the tallest isotope peak usually indicate in a simple mass spectrum?
คำตอบ
The most abundant isotope, assuming comparable detection response and singly charged ions.
การ์ด 35
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How much oxygen is present in 25.0 g of a compound that is 32.0% oxygen by mass?
คำตอบ
8.00 g O. Multiply 25.0 g by 0.320.
การ์ด 36
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What does a particle diagram with two unbonded species in changing ratios represent?
คำตอบ
A mixture, because more than one particle type is present and the ratio is not fixed in a formula unit.
การ์ด 37
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What distinguishes valence electrons from core electrons?
คำตอบ
Valence electrons are available for bonding or ion formation; main-group valence electrons occupy the outermost shell, while transition metals may also use (n−1)d electrons. Core electrons mainly shield nuclear charge.
การ์ด 38
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Why can PES peak groups reveal an atom's occupied subshells?
คำตอบ
Electrons in different subshells require distinct removal energies, producing separate binding-energy groups.
การ์ด 39
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How do ion radii compare with neutral atoms and within an isoelectronic series?
คำตอบ
Cations are smaller than their neutral atoms, while anions are larger. Among species with the same electron count, more protons pull the electrons closer and produce the smaller radius.
การ์ด 40
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What formula is expected for a compound between a Group 2 metal M and a Group 17 nonmetal X?
คำตอบ
MX₂, because M forms M²⁺ and X forms X⁻.
การ์ด 41
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When is a covalent bond considered nonpolar?
คำตอบ
When the bonded atoms have identical or very similar electronegativities, so the shared electron density is distributed approximately evenly.
การ์ด 42
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Why does a bonded pair of atoms have an equilibrium bond length?
คำตอบ
At that separation, attractive and repulsive interactions balance at minimum potential energy.
การ์ด 43
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How are particles arranged in an ionic solid?
คำตอบ
Cations and anions occupy a repeating three-dimensional lattice held by electrostatic attraction.
การ์ด 44
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What model explains bonding in a metal?
คำตอบ
Positive metal cores are held together by attraction to mobile, delocalized valence electrons.
การ์ด 45
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How do you construct a Lewis diagram?
คำตอบ
Count total valence electrons, adding electrons for a negative charge and subtracting them for a positive charge. Choose a skeleton, connect atoms with single bonds, complete terminal duets or octets, and place remaining electrons on the central atom. Add multiple bonds if needed, then check the electron total and formal charges.
การ์ด 46
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What does resonance mean in a molecule or ion?
คำตอบ
Resonance uses two or more valid Lewis diagrams with the same atom arrangement but different electron placement. The actual electron distribution is a hybrid; equivalent contributors have equal weight.
การ์ด 47
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What determines molecular shape in VSEPR theory?
คำตอบ
Electron domains around the central atom arrange to minimize repulsions.
การ์ด 48
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How does an ionic bond differ from a covalent bond?
คำตอบ
Ionic bonding is attraction among oppositely charged ions in an extended structure; covalent bonding uses shared electron density between atoms.
การ์ด 49
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What happens to potential energy when bonded atoms are pushed much closer than equilibrium?
คำตอบ
Potential energy rises sharply because nucleus–nucleus and electron–electron repulsions dominate.
การ์ด 50
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Why are many ionic solids brittle?
คำตอบ
A shifted lattice can align like charges, creating strong repulsion that splits the crystal.
การ์ด 51
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What molecular shapes arise from two electron domains with no lone pairs and from three domains with zero or one lone pair?
คำตอบ
Two bonding domains give linear with a 180° angle. Three domains with no lone pairs give trigonal planar with 120° angles; replacing one bond with a lone pair gives bent with an angle slightly below 120°.
การ์ด 52
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Why are metals electrically conductive as solids?
คำตอบ
Their delocalized electrons can move through the solid when an electric field is applied.
การ์ด 53
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How is formal charge calculated for an atom in a Lewis diagram?
คำตอบ
Formal charge = valence electrons − nonbonding electrons − half the bonding electrons.
การ์ด 54
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Why can't electronegativity difference alone classify a bond as ionic or covalent?
คำตอบ
Bonding lies on a continuum. A larger difference means more ionic character, but the element types and especially the compound's properties give the best classification.
การ์ด 55
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Which shapes and bond-angle trends arise as lone pairs replace bonds in four electron domains?
คำตอบ
Four bonds give tetrahedral with ideal 109.5° angles. One lone pair gives trigonal pyramidal with smaller angles; two lone pairs give bent with typically smaller angles again because lone pairs repel more strongly than bonding pairs.
การ์ด 56
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What feature of a potential-energy curve represents bond dissociation energy?
คำตอบ
The energy difference from the curve's minimum to the separated-atoms limit.
การ์ด 57
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When does an ionic compound conduct electricity?
คำตอบ
When molten or dissolved so its ions can move; not as a rigid solid lattice.
การ์ด 58
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What is a substitutional alloy?
คำตอบ
An alloy in which atoms of a similar size replace some host-metal atoms in the lattice.
การ์ด 59
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How do two, three, and four electron domains map to hybridization?
คำตอบ
Two domains map to sp, three to sp², and four to sp³, with ideal angles of 180°, 120°, and 109.5°. Hybridization involving d orbitals is outside this deck’s scope.
การ์ด 60
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What usually makes one resonance contributor more favorable than another?
คำตอบ
Smaller formal-charge magnitudes, appropriate negative charge on more electronegative atoms, and complete valence shells where applicable.
การ์ด 61
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How many sigma and pi bonds are in single, double, and triple bonds?
คำตอบ
A single bond has one sigma bond; a double has one sigma and one pi bond; a triple has one sigma and two pi bonds. Head-on sigma overlap is stronger than side-by-side pi overlap.
การ์ด 62
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Why is a polar covalent bond polar?
คำตอบ
Unequal electronegativity creates an uneven sharing of electron density and partial charges.
การ์ด 63
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Which molecular shapes arise as lone pairs replace bonds in five electron domains?
คำตอบ
Five bonds give trigonal bipyramidal; four bonds and one lone pair give seesaw; three bonds and two lone pairs give T-shaped; two bonds and three lone pairs give linear.
การ์ด 64
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How do ionic charge and ionic radius affect attraction between ions?
คำตอบ
Larger charge magnitudes and smaller ionic radii produce stronger attraction because the charge product increases and the ion centers are closer.
การ์ด 65
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Why do ionic solids often have high melting points?
คำตอบ
Many strong Coulombic attractions throughout the lattice must be overcome to free the ions.
การ์ด 66
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What is an interstitial alloy?
คำตอบ
A smaller atom occupies holes between host-metal atoms, often making lattice layers harder to slide.
การ์ด 67
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What shape has six bonding domains and no lone pairs on the central atom?
คำตอบ
Octahedral.
การ์ด 68
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Which elements commonly form incomplete octets in stable Lewis diagrams?
คำตอบ
Hydrogen forms a duet, and electron-deficient central atoms such as boron or beryllium can have fewer than eight electrons.
การ์ด 69
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How do bond order and atomic size affect covalent bond length and strength?
คำตอบ
Within a comparable bond family, higher bond order gives shorter, stronger bonds. Larger bonded atoms generally give longer bonds, which are often weaker because their orbitals overlap less effectively.
การ์ด 70
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What bonding model best fits a sample that is malleable and conducts as a solid?
คำตอบ
Metallic bonding with mobile, delocalized electrons and nondirectional attractions.
การ์ด 71
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What shape has six electron domains, five bonds, and one lone pair?
คำตอบ
Square pyramidal.
การ์ด 72
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Which lattice should have stronger attractions: MgO or NaCl, assuming similar separations?
คำตอบ
MgO, because the charge product for Mg²⁺ and O²⁻ is larger than for Na⁺ and Cl⁻.
การ์ด 73
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Why are pure metals often malleable?
คำตอบ
Metal cores can shift while the mobile electron sea maintains nondirectional attraction instead of exposing fixed like-charge planes.
การ์ด 74
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What is the best Lewis structure for CO₂?
คำตอบ
O=C=O, with two lone pairs on each oxygen and no formal charges.
การ์ด 75
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What shape has six electron domains, four bonds, and two opposite lone pairs?
คำตอบ
Square planar.
การ์ด 76
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What limitation does an odd total number of valence electrons create for a Lewis diagram?
คำตอบ
At least one electron must remain unpaired, so not every atom can have a complete paired-electron octet.
การ์ด 77
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What does a higher bond order do to a bond's potential-energy curve?
คำตอบ
It generally places the minimum at a shorter internuclear distance and makes the well deeper, corresponding to a shorter bond and a larger bond-dissociation energy.
การ์ด 78
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When can a carbon–carbon double bond produce geometric isomers?
คำตอบ
When each carbon has two different substituents. The pi bond restricts rotation, so distinct spatial arrangements can persist.
การ์ด 79
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When may a third-period central atom exceed an octet in a Lewis diagram?
คำตอบ
When the valid electron count and lower formal charges favor an expanded valence shell, as in species such as SF₆.
การ์ด 80
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How do you decide whether a molecule with polar bonds is polar overall?
คำตอบ
Add the bond-dipole vectors using the molecular shape; symmetry may cancel them, while an asymmetric arrangement leaves a net dipole.
การ์ด 81
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Which interparticle forces act between all atoms and molecules?
คำตอบ
London dispersion forces, caused by temporary and induced dipoles.
การ์ด 82
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What four broad solid types does this deck compare?
คำตอบ
Ionic, metallic, molecular, and covalent-network solids.
การ์ด 83
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How do gas particles differ from liquid particles?
คำตอบ
Gas particles are much farther apart and move independently; liquid particles stay close but can move past one another.
การ์ด 84
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What relationship connects pressure, volume, amount, and temperature for an ideal gas?
คำตอบ
PV = nRT, with absolute temperature in kelvins and units consistent with R.
การ์ด 85
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What does temperature measure in kinetic molecular theory?
คำตอบ
The particles' average translational kinetic energy.
การ์ด 86
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What two ideal-gas assumptions fail most clearly for real gases?
คำตอบ
Particles have nonzero volume and experience intermolecular attractions.
การ์ด 87
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How is molarity defined?
คำตอบ
Moles of solute per liter of solution: M = n/V.
การ์ด 88
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What must a correct particulate diagram of NaCl(aq) show?
คำตอบ
Separated Na⁺ and Cl⁻ ions in a 1:1 ratio, each surrounded by oriented water molecules.
การ์ด 89
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Which separation method removes an insoluble solid from a liquid?
คำตอบ
Filtration: the solid stays as residue while the liquid passes as filtrate.
การ์ด 90
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What does “like dissolves like” mean at the particle level?
คำตอบ
A solute tends to dissolve when new solute–solvent attractions can compete with the attractions disrupted in the pure substances.
การ์ด 91
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What happens when matter absorbs electromagnetic radiation?
คำตอบ
Its particles move to an allowed higher-energy state when the photon energy matches the energy gap.
การ์ด 92
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Which equations connect photon energy, frequency, and wavelength?
คำตอบ
E = hν and c = λν.
การ์ด 93
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What is the Beer–Lambert law?
คำตอบ
A = εbc: absorbance equals molar absorptivity at the chosen wavelength times path length times concentration.
การ์ด 94
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What molecular features generally strengthen London dispersion forces?
คำตอบ
More electrons and a more polarizable cloud strengthen temporary dipoles; greater contact area and accessible π-electron density can also strengthen the attraction.
การ์ด 95
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Why do molecular solids usually have low melting points and fail to conduct electricity?
คำตอบ
Distinct molecules are held together by relatively weak intermolecular forces, while their valence electrons stay localized in bonds and lone pairs.
การ์ด 96
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How do particles move in a solid?
คำตอบ
They vibrate about fixed positions and do not translate past one another.
การ์ด 97
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What graph shapes connect V or P with T(K) or n for an ideal gas?
คำตอบ
All four are straight lines through the origin: V versus T(K) at fixed n and P; P versus T(K) at fixed n and V; V versus n at fixed P and T; and P versus n at fixed V and T.
การ์ด 98
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At the same temperature, which gas has the greater average molecular speed: He or Xe?
คำตอบ
He. Both have the same average kinetic energy, but KE = ½mv² means the lower-mass particles move faster.
การ์ด 99
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Why do real gases deviate more at high pressure?
คำตอบ
Particles are crowded, so their own volume is no longer negligible compared with the container volume.
การ์ด 100
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Which relationship describes dilution when solute amount is conserved?
คำตอบ
M₁V₁ = M₂V₂.
การ์ด 101
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Why does an aqueous ionic solution conduct electricity?
คำตอบ
Dissolved ions are mobile and carry charge through the solution.
การ์ด 102
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Which property lets simple distillation separate two liquids?
คำตอบ
A sufficient difference in volatility or boiling point, so the vapor is enriched in the more volatile component.
การ์ด 103
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Why are many ionic compounds soluble in water but poorly soluble in a nonpolar solvent?
คำตอบ
Water can form strong ion–dipole attractions that stabilize separated ions; a nonpolar solvent cannot provide comparable attractions.
การ์ด 104
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Which molecular transition is commonly associated with microwave absorption?
คำตอบ
A transition between quantized rotational energy levels.
การ์ด 105
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What frequency corresponds to a 600. nm photon?
คำตอบ
5.00 × 10^14 s^-1. Use ν = c/λ with 600. nm = 6.00 × 10^-7 m.
การ์ด 106
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What is the absorbance to two significant figures when ε = 2.0 × 10² L mol^-1 cm^-1, b = 1.00 cm, and c = 0.0020 M?
คำตอบ
0.40. Use A = εbc.
การ์ด 107
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What conditions allow hydrogen bonding between two molecules?
คำตอบ
One molecule must donate an H covalently bonded to N, O, or F, and the other must provide a lone pair on N, O, or F. A molecule can be a donor, an acceptor, or both.
การ์ด 108
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Why are covalent-network solids often very hard with high melting points?
คำตอบ
A continuous network of strong covalent bonds must be disrupted to deform or melt the solid.
การ์ด 109
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Why do a substance's solid and liquid phases usually have similar molar volumes?
คำตอบ
Their particles remain in close contact in both phases, even though liquid particles can move past one another.
การ์ด 110
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How is a gas mixture's total pressure related to its component pressures?
คำตอบ
Ptotal = ΣPi; each partial pressure is the pressure that component would exert alone in the same volume and temperature.
การ์ด 111
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What microscopic events create gas pressure?
คำตอบ
Gas particles collide with container walls and transfer momentum.
การ์ด 112
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Why do intermolecular attractions matter more for gases at low temperature?
คำตอบ
Particles move more slowly, so attractions can alter their paths and promote condensation.
การ์ด 113
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What is the final concentration after 50.0 mL of 2.00 M solution is diluted to 200.0 mL?
คำตอบ
0.500 M. Use M₂ = M₁V₁/V₂.
การ์ด 114
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What must a particulate representation of a solution communicate?
คำตอบ
The relative concentrations of its components and the particle-level interactions among those components.
การ์ด 115
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What causes components to separate in chromatography?
คำตอบ
They differ in attraction to the stationary phase and the mobile phase, so they travel at different rates.
การ์ด 116
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Why are many polar molecular solutes soluble in water?
คำตอบ
Dipole attractions or hydrogen bonds with water can replace the solute–solute and water–water attractions disrupted during mixing.
การ์ด 117
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Why does an atom produce discrete spectral lines?
คำตอบ
Its electrons can occupy only quantized energy levels, so only photons matching allowed energy differences are absorbed or emitted.
การ์ด 118
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How does photon energy change when frequency doubles?
คำตอบ
It doubles because E = hν.
การ์ด 119
คำถาม
Why is a calibration curve useful in spectrophotometry?
คำตอบ
It relates measured absorbance to known concentrations, letting an unknown concentration be read by interpolation within the linear range.
การ์ด 120
คำถาม
How does an ion–dipole attraction form, and how does it compare with dipole–dipole attraction?
คำตอบ
An ion attracts the oppositely charged end of a polar molecule. Ion–dipole attractions tend to be stronger than dipole–dipole attractions.
การ์ด 121
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Which solid type is usually both conductive and malleable?
คำตอบ
A metallic solid, because its delocalized electrons move and its nondirectional bonding tolerates layer shifts.
การ์ด 122
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How does a crystalline solid differ from an amorphous solid?
คำตอบ
A crystalline solid has long-range repeating order; an amorphous solid lacks that long-range periodic arrangement.
การ์ด 123
คำถาม
How is a gas component's partial pressure found from mole fraction?
คำตอบ
Pi = XiPtotal.
การ์ด 124
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How does heating a fixed-volume gas affect its pressure in the ideal model?
คำตอบ
Pressure rises because faster particles collide with the walls more forcefully and frequently.
การ์ด 125
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Why can attractions make a real gas's measured pressure lower than the ideal prediction?
คำตอบ
Attractions pull approaching particles away from the walls, reducing momentum transfer during wall collisions.
การ์ด 126
คำถาม
How many moles of ions result from complete dissolution of 0.20 mol CaCl₂?
คำตอบ
0.60 mol ions: 0.20 mol Ca²⁺ plus 0.40 mol Cl⁻.
การ์ด 127
คำถาม
How should water orient around Cl⁻ in a particle model?
คำตอบ
Its partially positive hydrogen ends point toward Cl⁻.
การ์ด 128
คำถาม
Can filtration separate dissolved components of a liquid solution?
คำตอบ
No. Dissolved particles pass through the filter with the solvent; filtration only retains an insoluble solid.
การ์ด 129
คำถาม
Why do nonpolar molecular solutes often dissolve in nonpolar solvents?
คำตอบ
Both rely mainly on compatible London dispersion forces, so mixing can replace the attractions disrupted in the separate substances.
การ์ด 130
คำถาม
What does a shorter absorbed wavelength imply about an energy transition?
คำตอบ
A larger energy gap because E = hc/λ.
การ์ด 131
คำถาม
What is the energy of a photon with frequency 5.0 × 10^14 s^-1?
คำตอบ
3.3 × 10^-19 J. Multiply by Planck's constant: E = (6.626 × 10^-34 J·s)(5.0 × 10^14 s^-1).
การ์ด 132
คำถาม
How does doubling cuvette path length affect absorbance in the linear Beer–Lambert range?
คำตอบ
Absorbance doubles if concentration and molar absorptivity stay constant.
การ์ด 133
คำถาม
How can noncovalent interactions affect a large biomolecule?
คำตอบ
Attractions between molecules or between different regions of the same molecule help set its shape, which strongly affects its properties and function.
การ์ด 134
คำถาม
Why does an ionic solid usually fail to conduct as a solid?
คำตอบ
Its ions are fixed in lattice positions. The same substance conducts when molten or dissolved because the ions can then move.
การ์ด 135
คำถาม
Why does a gas have no definite shape or volume?
คำตอบ
Its widely spaced particles move constantly and experience minimal interparticle attraction, so they spread through the available container.
การ์ด 136
คำถาม
What graph shapes show the inverse pressure–volume relationship for a fixed amount of ideal gas at constant temperature?
คำตอบ
A plot of P against V is a decreasing curve, while P against 1/V is a straight line through the origin.
การ์ด 137
คำถาม
At the same temperature, do different ideal gases have different average kinetic energies?
คำตอบ
No. Average translational kinetic energy depends only on absolute temperature.
การ์ด 138
คำถาม
Under which conditions is ideal-gas behavior most accurate?
คำตอบ
Low pressure and high temperature, where particles are far apart and attractions matter least.
การ์ด 139
คำถาม
What particle-level feature distinguishes a solution from a heterogeneous mixture?
คำตอบ
A solution—whether solid, liquid, or gas—is uniform throughout; a heterogeneous mixture has regions or phases with different compositions.
การ์ด 140
คำถาม
How should water orient around Na⁺ in a particulate model?
คำตอบ
Its partially negative oxygen end points toward Na⁺.
การ์ด 141
คำถาม
In paper chromatography, why does one solute spot travel farther than another?
คำตอบ
It interacts more strongly with the mobile phase or more weakly with the stationary phase. With known phase polarities, that travel difference can reveal relative solute polarity.
การ์ด 142
คำถาม
What energy competition helps explain whether an ionic solid dissolves?
คำตอบ
The energy needed to separate lattice ions competes with the energy released when ion–solvent attractions form.
การ์ด 143
คำถาม
Which molecular motions commonly absorb infrared radiation?
คำตอบ
Bond vibrations whose changing dipole can interact with the radiation.
การ์ด 144
คำถาม
Why must wavelength be converted to meters in c = λν when c is in m s^-1?
คำตอบ
Consistent units are required so meters cancel correctly and frequency comes out in s^-1.
การ์ด 145
คำถาม
How can fingerprints on a cuvette affect a visible-light absorbance reading?
คำตอบ
They can absorb or scatter extra light, making measured absorbance too high and the inferred concentration too high.
การ์ด 146
คำถาม
What causes and controls the strength of dipole–dipole attractions?
คำตอบ
Opposite partial charges on neighboring polar molecules attract. Strength increases with larger molecular dipoles and depends on how favorably the dipoles are oriented.
การ์ด 147
คำถาม
Why is graphite conductive and soft while diamond is insulating and hard?
คำตอบ
Graphite has delocalized electrons within its sheets, so it conducts, and its layers can slide, so it is soft. Diamond has a rigid three-dimensional network of localized covalent bonds, making it hard and insulating.
การ์ด 148
คำถาม
Why are gases much more compressible than liquids?
คำตอบ
Gas particles have large empty spaces between them; liquid particles are already close together.
การ์ด 149
คำถาม
What volume does 0.500 mol CO₂ occupy at 1.00 atm and 300. K if it behaves ideally?
คำตอบ
12.3 L. Use V = nRT/P = (0.500 mol)(0.08206 L atm mol^-1 K^-1)(300. K)/(1.00 atm).
การ์ด 150
คำถาม
Why does a lighter gas effuse faster than a heavier gas at the same temperature?
คำตอบ
Its particles have a higher average speed because equal average kinetic energy is shared by less mass.
การ์ด 151
คำถาม
How does finite particle volume affect a real gas at very high pressure?
คำตอบ
The free volume available for particle motion is smaller than the container volume assumed by the ideal model.
การ์ด 152
คำถาม
How should 250.0 mL of 0.100 M NaCl be prepared from solid NaCl?
คำตอบ
Dissolve 0.0250 mol NaCl, or 1.46 g, then dilute to exactly 250.0 mL in a volumetric flask.
การ์ด 153
คำถาม
What changes in a particle diagram when a solution is diluted without losing solute?
คำตอบ
The solute-particle count stays constant while solvent volume and particle spacing increase.
การ์ด 154
คำถาม
Why is fractional distillation better than simple distillation for liquids with close boiling points?
คำตอบ
Repeated vaporization–condensation steps enrich the vapor in the more volatile component more effectively.
การ์ด 155
คำถาม
Why are oil and water usually immiscible?
คำตอบ
Water's strong hydrogen-bond network isn't replaced by equally strong water–oil attractions, so the substances separate into phases.
การ์ด 156
คำถาม
Which molecular transition is commonly associated with ultraviolet or visible absorption?
คำตอบ
A transition between electronic energy levels.
การ์ด 157
คำถาม
Which photon carries more energy, blue light or red light?
คำตอบ
Blue light, because it has shorter wavelength and higher frequency.
การ์ด 158
คำถาม
Why is absorbance often measured at the wavelength of maximum absorbance in Beer–Lambert analysis?
คำตอบ
It gives the largest concentration-sensitive signal, and the flat top near the maximum makes small wavelength-setting errors less influential.
การ์ด 159
คำถาม
What creates a dipole–induced-dipole attraction, and what controls its strength?
คำตอบ
A permanent dipole distorts a nearby nonpolar particle's electron cloud and creates an attractive temporary dipole. A larger permanent dipole and a more polarizable nonpolar partner make the attraction stronger.
การ์ด 160
คำถาม
How do stronger intermolecular forces affect vapor pressure, boiling point, and melting point?
คำตอบ
They lower vapor pressure and raise boiling point. Melting point often rises too, but the trend is less direct because melting rearranges rather than fully separates particles.
การ์ด 161
คำถาม
How do particles behave in a liquid?
คำตอบ
They stay in close contact while moving and colliding continuously. Temperature and interparticle attractions affect their arrangement and motion.
การ์ด 162
คำถาม
Why must Celsius temperature be converted to kelvins in gas-law calculations?
คำตอบ
Gas-law proportionalities require an absolute temperature scale whose zero corresponds to zero extrapolated thermal motion.
การ์ด 163
คำถาม
How does raising temperature change a Maxwell–Boltzmann speed distribution?
คำตอบ
The distribution broadens, its peak lowers and shifts right, and a larger fraction of particles have high speed.
การ์ด 164
คำถาม
Why does the ideal-gas model treat collisions as elastic?
คำตอบ
It assumes total kinetic energy is conserved in particle–particle and particle–wall collisions.
การ์ด 165
คำถาม
How many moles of solute are in 75.0 mL of a 0.400 M solution?
คำตอบ
0.0300 mol. Multiply 0.400 mol L^-1 by 0.0750 L.
การ์ด 166
คำถาม
For equal solution volumes drawn at the same scale, what shows which solution is more concentrated?
คำตอบ
The more concentrated diagram contains more solute particles in that equal volume.
การ์ด 167
คำถาม
How do differences in intermolecular attractions let distillation separate a liquid solution?
คำตอบ
They give the components different vapor pressures, so the vapor is enriched in the more volatile component.
การ์ด 168
คำถาม
What comparison helps predict whether two liquids will be miscible?
คำตอบ
Liquids with similar types and strengths of intermolecular attractions are more likely to mix uniformly.
การ์ด 169
คำถาม
How can an absorption spectrum help identify a substance?
คำตอบ
Its allowed energy gaps produce a characteristic pattern of absorbed wavelengths that can be compared with known spectra.
การ์ด 170
คำถาม
How does absorbing or emitting a photon change an atom's or molecule's energy?
คำตอบ
Absorption raises the species' energy by exactly the photon energy; emission lowers it by the same amount.
การ์ด 171
คำถาม
What macroscopic evidence can support that a chemical reaction occurred?
คำตอบ
Evidence can include gas formation, precipitate formation, a persistent color change, or an energy change, interpreted with particle-level changes.
การ์ด 172
คำถาม
What does a net ionic equation include?
คำตอบ
Only the dissolved or reacting species that undergo chemical change; spectator ions are omitted.
การ์ด 173
คำถาม
What must a correct particulate reaction diagram conserve?
คำตอบ
The number of atoms of every element and the total charge.
การ์ด 174
คำถาม
What distinguishes a chemical change from a physical change?
คำตอบ
A chemical change rearranges bonds into new substances; a physical change alters state or arrangement without changing chemical identity.
การ์ด 175
คำถาม
What does a balanced equation's coefficient ratio provide?
คำตอบ
The mole ratio among reacting and produced species.
การ์ด 176
คำถาม
What is the equivalence point of a titration?
คำตอบ
The point where titrant and analyte have reacted in the stoichiometric ratio given by the balanced equation.
การ์ด 177
คำถาม
What defines a precipitation reaction?
คำตอบ
Aqueous ions combine to form a sparingly soluble solid.
การ์ด 178
คำถาม
What happens in a Brønsted–Lowry acid–base reaction?
คำตอบ
A proton transfers from the acid (donor) to the base (acceptor). In aqueous solution, H₂O can play either role.
การ์ด 179
คำถาม
What does oxidation mean in a redox reaction?
คำตอบ
Loss of electrons and an increase in oxidation number.
การ์ด 180
คำถาม
What particle-level change confirms that a process is chemical?
คำตอบ
Atoms rearrange into new combinations, producing substances with different compositions.
การ์ด 181
คำถาม
Which ions are spectators when AgNO₃(aq) reacts with NaCl(aq)?
คำตอบ
Na⁺ and NO₃⁻. The net ionic reaction is Ag⁺(aq) + Cl⁻(aq) → AgCl(s).
การ์ด 182
คำถาม
How does a particulate diagram reveal the limiting reactant?
คำตอบ
After forming the maximum product allowed by the ratio, none of the limiting reactant remains while excess reactant particles do.
การ์ด 183
คำถาม
Is melting ice a chemical or physical change?
คำตอบ
A physical change. H₂O molecules remain H₂O while their arrangement and motion change.
การ์ด 184
คำถาม
How is the limiting reactant identified from given amounts?
คำตอบ
Convert each reactant to the same product amount using the balanced equation; the smaller product amount identifies the limiting reactant.
การ์ด 185
คำถาม
How does an endpoint differ from an equivalence point?
คำตอบ
The endpoint is an observed signal such as indicator color change; the equivalence point is the exact stoichiometric condition.
การ์ด 186
คำถาม
How is complete combustion of a hydrocarbon in excess oxygen classified, and what products form?
คำตอบ
It is a redox combustion reaction that forms CO₂ and H₂O.
การ์ด 187
คำถาม
What are the conjugate acid and conjugate base in NH₃ + H₂O ⇌ NH₄⁺ + OH⁻?
คำตอบ
NH₄⁺ is the conjugate acid of NH₃, and OH⁻ is the conjugate base of H₂O.
การ์ด 188
คำถาม
What does reduction mean in a redox reaction?
คำตอบ
Gain of electrons and a decrease in oxidation number.
การ์ด 189
คำถาม
Which common changes are physical rather than chemical?
คำตอบ
Phase changes and the formation or separation of mixtures are physical when each substance keeps its composition.
การ์ด 190
คำถาม
How are strong soluble electrolytes written in a complete ionic equation?
คำตอบ
As separated aqueous ions; solids, liquids, gases, and weak electrolytes stay intact.
การ์ด 191
คำถาม
A diagram starts with six A particles and four B₂ particles for 2A + B₂ → 2AB; what remains after completion?
คำตอบ
One B₂ remains. Six A consume three B₂ and form six AB.
การ์ด 192
คำถาม
Why is dissolving NaCl in water normally classified as a physical change?
คำตอบ
Na⁺ and Cl⁻ separate and become hydrated, but retain their chemical identities. Removing the water recovers NaCl; the shift from ion–ion to ion–dipole attractions does not by itself form a new substance.
การ์ด 193
คำถาม
What mass of AgCl can form from 25.0 mL of 0.200 M AgNO₃ mixed with excess Cl⁻?
คำตอบ
0.717 g AgCl. The 1:1 reaction gives 0.00500 mol AgCl; multiply by 143.32 g mol^-1.
การ์ด 194
คำถาม
What calculation finds unknown analyte moles at equivalence?
คำตอบ
Use titrant moles, n = MV, then apply the balanced-reaction mole ratio.
การ์ด 195
คำถาม
Which feature identifies an acid–base, redox, or precipitation reaction?
คำตอบ
Acid–base reactions transfer protons, redox reactions change oxidation numbers through electron transfer, and precipitation reactions form a sparingly soluble solid.
การ์ด 196
คำถาม
What is the net ionic equation for strong acid–strong base neutralization?
คำตอบ
H⁺(aq) + OH⁻(aq) → H₂O(l).
การ์ด 197
คำถาม
What is the oxidation number of sulfur in SO₄²⁻?
คำตอบ
+6. Four oxygens contribute -8 total, so sulfur must be +6 to give -2 overall.
การ์ด 198
คำถาม
Why can gas bubbles alone be ambiguous evidence of reaction?
คำตอบ
Bubbles may also come from boiling or dissolved gas escaping, so the context and particle identities must support a chemical change.
การ์ด 199
คำถาม
How is melting ice represented as a balanced physical-change equation?
คำตอบ
H₂O(s) → H₂O(l). The formula and atom count stay the same because only the physical state changes.
การ์ด 200
คำถาม
What does a particle diagram show when no reaction occurs after two aqueous ionic solutions mix?
คำตอบ
All ions remain separated and solvated, with no new bonded particles, precipitate, or gas.
การ์ด 201
คำถาม
Why is rusting iron a chemical change?
คำตอบ
Iron atoms form new iron-oxide substances through electron transfer and new bonding.
การ์ด 202
คำถาม
For 2H₂O₂(aq) → 2H₂O(l) + O₂(g), what volume of O₂ forms from 0.100 mol H₂O₂ at 298 K and 1.00 atm?
คำตอบ
1.22 L O₂. The mole ratio gives 0.0500 mol O₂, then V = nRT/P.
การ์ด 203
คำถาม
A 25.0 mL monoprotic acid sample requires 20.0 mL of 0.150 M NaOH; what is the acid concentration?
คำตอบ
0.120 M. At 1:1 equivalence, moles acid = 0.0200 L × 0.150 M, then divide by 0.0250 L.
การ์ด 204
คำถาม
Which salts does the minimum solubility rule in this deck treat as soluble?
คำตอบ
All salts containing Na⁺, K⁺, NH₄⁺, or NO₃⁻ are treated as soluble in water.
การ์ด 205
คำถาม
How are the strengths of a conjugate acid and its conjugate base related?
คำตอบ
A stronger acid has a weaker conjugate base, and a stronger base has a weaker conjugate acid.
การ์ด 206
คำถาม
How are oxidation and reduction half-reactions combined into one balanced equation?
คำตอบ
Multiply them so electrons lost equal electrons gained, add the half-reactions, then cancel electrons and any identical species on both sides.
การ์ด 207
คำถาม
How do molecular, complete ionic, and net ionic equations differ?
คำตอบ
Molecular equations keep compounds intact, complete ionic equations split strong soluble electrolytes, and net ionic equations remove spectators. All three conserve atoms and charge.
การ์ด 208
คำถาม
How should coefficients change particle counts in a reaction diagram?
คำตอบ
They set whole-particle ratios while preserving each particle's chemical formula.
การ์ด 209
คำถาม
Is separating a mixture by distillation a chemical or physical change?
คำตอบ
A physical change. Components change phase and location but keep their chemical identities.
การ์ด 210
คำถาม
What equation results from Cu → Cu²⁺ + 2e⁻ and Ag⁺ + e⁻ → Ag?
คำตอบ
Cu + 2Ag⁺ → Cu²⁺ + 2Ag. Multiply the silver half-reaction by 2 and cancel 2e⁻; both atom counts and net charge then match.
การ์ด 211
คำถาม
How is average reaction rate found from a reactant concentration?
คำตอบ
Use the negative concentration change divided by elapsed time, adjusted by its stoichiometric coefficient when comparing species rates.
การ์ด 212
คำถาม
What does a rate law express?
คำตอบ
It shows how the measured rate depends on reactant concentrations. In rate = k[A]^m[B]^n, m and n are the orders in A and B, and m + n is the overall order.
การ์ด 213
คำถาม
A plot of ln[A] versus time is linear; what is the order in A and its integrated rate law?
คำตอบ
First order: ln[A]t = ln[A]0 − kt, so the plot's slope is −k.
การ์ด 214
คำถาม
What is an elementary reaction?
คำตอบ
A single step in a mechanism whose rate law follows directly from its reactant molecularity.
การ์ด 215
คำถาม
What two collision conditions are needed for reaction?
คำตอบ
Sufficient collision energy and a productive molecular orientation.
การ์ด 216
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What does activation energy represent on a reaction-energy profile?
คำตอบ
The energy difference from the reactants to the transition state. The reaction coordinate tracks the step's structural progress, not elapsed time.
การ์ด 217
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What must the elementary steps of a valid mechanism do when added?
คำตอบ
Cancel intermediates and reproduce the overall balanced reaction.
การ์ด 218
คำถาม
How is a proposed mechanism tested against kinetics?
คำตอบ
Its derived rate law must agree with the experimentally measured rate law.
การ์ด 219
คำถาม
What does a pre-equilibrium approximation assume?
คำตอบ
A fast reversible step reaches equilibrium before a later slow step consumes its intermediate.
การ์ด 220
คำถาม
What does each peak on a multistep energy profile represent?
คำตอบ
A transition state for one elementary step.
การ์ด 221
คำถาม
How does a catalyst increase reaction rate?
คำตอบ
It provides an alternate mechanism with a lower activation-energy pathway.
การ์ด 222
คำถาม
Why does crushing a solid reactant usually increase its reaction rate?
คำตอบ
Crushing increases exposed surface area, so more reactant particles can collide with the other reactant each second.
การ์ด 223
คำถาม
How is reaction order found from initial-rate data?
คำตอบ
Compare trials where one reactant concentration changes while the others stay constant, then match the rate factor to the concentration factor.
การ์ด 224
คำถาม
A plot of [A] versus time is linear; what is the order in A and its integrated rate law?
คำตอบ
Zero order: [A]t = [A]0 − kt, so the plot's slope is −k.
การ์ด 225
คำถาม
What is the rate law for the elementary step 2A + B → products?
คำตอบ
rate = k[A]²[B]. This inference is valid because the step is elementary.
450 การ์ด
AP Chemistry Flashcards: Complete 9-Unit Course Review
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การ์ด 226
คำถาม
How does raising temperature change a Maxwell–Boltzmann energy distribution and reaction rate?
คำตอบ
The distribution shifts and broadens toward higher energies, so a larger fraction of collisions exceeds the activation-energy threshold and can react.
การ์ด 227
คำถาม
How is ΔH read from a reaction-energy profile?
คำตอบ
ΔH = energy of products − energy of reactants.
การ์ด 228
คำถาม
What is a reaction intermediate?
คำตอบ
A species formed in one mechanism step and consumed in a later step, so it cancels from the overall equation.
การ์ด 229
คำถาม
Why can't overall reaction coefficients usually supply rate-law exponents?
คำตอบ
The overall equation hides the mechanism; exponents come from experiment unless the reaction is a stated elementary step.
การ์ด 230
คำถาม
How does pre-equilibrium remove an intermediate from a rate law?
คำตอบ
Use the fast-step equilibrium relation to express the intermediate concentration in terms of stable reactants.
การ์ด 231
คำถาม
What does each valley between peaks represent on a multistep profile?
คำตอบ
A reaction intermediate.
การ์ด 232
คำถาม
Does a catalyst change ΔH or the equilibrium constant?
คำตอบ
No. It changes the pathway and rates, not reactant/product energies or the equilibrium composition.
การ์ด 233
คำถาม
For 2A → B, how are disappearance of A and appearance of B related?
คำตอบ
Reaction rate = -(1/2)Δ[A]/Δt = Δ[B]/Δt.
การ์ด 234
คำถาม
How do the units of k depend on a rate law's overall order?
คำตอบ
They must make the rate unit M s^-1: zero order uses M s^-1, first order s^-1, and second order M^-1 s^-1.
การ์ด 235
คำถาม
A plot of 1/[A] versus time is linear; what is the order in A and its integrated rate law?
คำตอบ
Second order: 1/[A]t = 1/[A]0 + kt, so the plot's slope is +k.
การ์ด 236
คำถาม
What is molecularity?
คำตอบ
The number of reacting particles in an elementary step, such as unimolecular or bimolecular.
การ์ด 237
คำถาม
How does raising temperature affect k in the qualitative Arrhenius model?
คำตอบ
k increases, often sharply, because a larger fraction of collisions can reach the transition state. Arrhenius-equation calculations are outside this deck’s scope.
การ์ด 238
คำถาม
A reactant falls from 0.80 M to 0.50 M in 30. s; what is its average disappearance rate to two significant figures?
คำตอบ
0.010 M s^-1. Use -(0.50 − 0.80) M ÷ 30. s.
การ์ด 239
คำถาม
How does a catalyst differ from an intermediate in a mechanism?
คำตอบ
A catalyst is consumed early and regenerated later; an intermediate is formed early and consumed later.
การ์ด 240
คำถาม
For 2NO₂ → NO₃ + NO (slow), followed by NO₃ + CO → NO₂ + CO₂ (fast), what rate law is predicted?
คำตอบ
rate = k[NO₂]². The first step is elementary and rate-limiting, so its molecularity sets the observed rate law.
การ์ด 241
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On a multistep reaction-energy profile, which feature often identifies the rate-determining step?
คำตอบ
The step with the largest activation barrier measured from its preceding valley to its peak.
การ์ด 242
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If changing [B] leaves rate unchanged, what is the order in B?
คำตอบ
Zero order, so [B]^0 = 1 in the measured rate law.
การ์ด 243
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What mechanism changes can binding, acid–base, or surface catalysis introduce?
คำตอบ
They can orient reactants, lower activation barriers, or create new bound, protonated, or deprotonated intermediates and elementary steps; the catalyst is regenerated.
การ์ด 244
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What is special about a first-order reaction's half-life?
คำตอบ
It is constant and independent of starting concentration: t1/2 = ln 2/k. Radioactive decay is a common first-order example.
การ์ด 245
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Why is a termolecular elementary collision uncommon?
คำตอบ
Three particles must collide simultaneously with suitable energy and orientation, which is much less probable than one- or two-particle events.
การ์ด 246
คำถาม
On a reaction-energy profile, how are reverse activation energy, forward activation energy, and ΔH related?
คำตอบ
Ea,reverse = Ea,forward − ΔH. The reverse barrier is measured from products to the same transition state.
การ์ด 247
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Why can correct orientation matter even above the activation energy?
คำตอบ
The colliding reactive sites must align so old bonds can break and new bonds can form along the reaction pathway.
การ์ด 248
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How does detecting a proposed reaction intermediate affect a mechanism claim?
คำตอบ
It supports a mechanism that contains that intermediate, but it doesn't prove that mechanism is unique.
การ์ด 249
คำถาม
For 2NO ⇌ N₂O₂ (fast equilibrium), followed by N₂O₂ + O₂ → 2NO₂ (slow), what observed rate law results?
คำตอบ
rate = kobs[NO]²[O₂]. Start with rate = k₂[N₂O₂][O₂], use [N₂O₂] = K[NO]² from the fast equilibrium, then substitute.
การ์ด 250
คำถาม
What does the highest point of a one-step energy profile represent?
คำตอบ
The transition state, an unstable arrangement at the top of the activation barrier.
การ์ด 251
คำถาม
What sign does q have for an endothermic system?
คำตอบ
Positive, because the system absorbs heat from the surroundings.
การ์ด 252
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How does an exothermic reaction appear on an enthalpy diagram?
คำตอบ
Products lie below reactants, so ΔH is negative.
การ์ด 253
คำถาม
What condition defines thermal equilibrium?
คำตอบ
Objects in contact have the same temperature, so there is no net heat transfer.
การ์ด 254
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What equations relate heat capacity and temperature change to heat transfer?
คำตอบ
Use q = mcΔT with specific heat capacity, or q = nCₘΔT with molar heat capacity.
การ์ด 255
คำถาม
Why is temperature constant during a phase-change plateau?
คำตอบ
Added or removed energy changes interparticle potential energy instead of average kinetic energy.
การ์ด 256
คำถาม
What does ΔHrxn describe?
คำตอบ
The heat absorbed or released at constant pressure for the reaction exactly as written under the stated conditions.
การ์ด 257
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How is reaction enthalpy estimated from average bond enthalpies?
คำตอบ
ΔHrxn ≈ Σ(bonds broken) − Σ(bonds formed).
การ์ด 258
คำถาม
What is the standard enthalpy of formation of an element in its standard state?
คำตอบ
Zero by definition.
การ์ด 259
คำถาม
In a Hess’s law calculation, how should a step change when the target needs twice its reverse?
คำตอบ
Reverse the equation, double every coefficient, and multiply its ΔH by -2.
การ์ด 260
คำถาม
How can energy cross a system boundary during a process?
คำตอบ
As heat or work. Heat transferred to or work done on the system increases its energy; heat transferred from or work done by the system decreases it.
การ์ด 261
คำถาม
How does an endothermic reaction appear on an enthalpy diagram?
คำตอบ
Products lie above reactants, so ΔH is positive.
การ์ด 262
คำถาม
How are heat gained by a system and heat lost by its surroundings related in an isolated setup?
คำตอบ
qsystem = -qsurroundings.
การ์ด 263
คำถาม
In coffee-cup calorimetry, how is reaction heat related to solution heat?
คำตอบ
qrxn = -qsolution when calorimeter heat is negligible and pressure is constant.
การ์ด 264
คำถาม
What heat is required to melt n moles at the melting point?
คำตอบ
q = nΔHfus.
การ์ด 265
คำถาม
How does reversing a reaction change ΔH?
คำตอบ
It reverses the sign of ΔH.
การ์ด 266
คำถาม
Why is breaking a bond endothermic?
คำตอบ
Energy must be supplied to separate atoms against their bonding attraction.
การ์ด 267
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How is ΔH°rxn calculated from standard enthalpies of formation?
คำตอบ
ΣνΔHf°(products) − ΣνΔHf°(reactants).
การ์ด 268
คำถาม
How does multiplying an equation by 3 affect its ΔH?
คำตอบ
Multiply ΔH by 3 because enthalpy change scales with reaction amount.
การ์ด 269
คำถาม
Why can an exothermic dissolution warm the solution?
คำตอบ
The solution warms because forming solute–solvent attractions releases more energy than is absorbed in separating the original particles. The net potential-energy decrease raises particle kinetic energy and temperature.
การ์ด 270
คำถาม
Does an energy diagram's activation barrier determine ΔH?
คำตอบ
No. ΔH depends on reactant and product energy levels, while the barrier controls kinetics.
การ์ด 271
คำถาม
Why does heat flow from a warmer object to a cooler object?
คำตอบ
Energy transfers through collisions until their average kinetic energies, and therefore temperatures, equalize.
การ์ด 272
คำถาม
How much heat warms 100.0 g of water by 5.0°C?
คำตอบ
2.1 kJ. Use q = (100.0 g)(4.184 J g^-1 °C^-1)(5.0°C).
การ์ด 273
คำถาม
How are the molar enthalpies of a phase change and its reverse related?
คำตอบ
They have equal magnitudes and opposite signs, such as ΔHcond = -ΔHvap and ΔHfreeze = -ΔHfus.
การ์ด 274
คำถาม
How does doubling every coefficient in a thermochemical equation affect ΔH?
คำตอบ
It doubles ΔH.
การ์ด 275
คำถาม
Why is forming a bond exothermic?
คำตอบ
Atoms move to a lower-potential-energy bonded arrangement and release energy.
การ์ด 276
คำถาม
What formation equation defines ΔHf° for CO₂(g)?
คำตอบ
C(s, graphite) + O₂(g) → CO₂(g), forming exactly one mole from elements in standard states.
การ์ด 277
คำถาม
What should happen to intermediate species when equations in a Hess’s law calculation are added?
คำตอบ
They cancel, leaving the target overall reaction.
การ์ด 278
คำถาม
If the surroundings warm during a process, what is the likely sign of qsystem?
คำตอบ
Negative; the system likely released heat to the surroundings.
การ์ด 279
คำถาม
For a profile with reactants at 40 kJ and products at 10 kJ, what is ΔH?
คำตอบ
-30 kJ for the reaction as drawn.
การ์ด 280
คำถาม
Assuming no phase change, what determines the final temperature when two substances exchange heat in an insulated container?
คำตอบ
Energy conservation: q_warm + q_cool = 0. Use each substance's mass, heat capacity, and initial temperature to solve for the common final temperature.
การ์ด 281
คำถาม
How would heat loss to the room affect an exothermic calorimetry result?
คำตอบ
The observed temperature rise is too small, so the calculated magnitude of released heat is too low.
การ์ด 282
คำถาม
What heat expression covers warming a liquid without a phase change?
คำตอบ
q = mcΔT, not nΔHphase.
การ์ด 283
คำถาม
If forming 1 mol of product has ΔH = -50 kJ mol^-1, what is q when 2 mol forms?
คำตอบ
-100 kJ. Use q = nΔH = (2 mol)(-50 kJ mol^-1).
การ์ด 284
คำถาม
Breaking reactant bonds requires 500 kJ, and forming product bonds releases 650 kJ; what is the estimated ΔH?
คำตอบ
-150 kJ, from 500 − 650.
การ์ด 285
คำถาม
For CO(g) + ½O₂(g) → CO₂(g), what is ΔH°rxn if ΔHf°[CO] = -110.5 and ΔHf°[CO₂] = -393.5 kJ mol^-1?
คำตอบ
-283.0 kJ. Use -393.5 - [-110.5 + ½(0)], since ΔHf°[O₂(g)] = 0.
การ์ด 286
คำถาม
In a Hess’s law calculation, two valid steps have ΔH values +25 kJ and -60 kJ; what is the combined ΔH?
คำตอบ
-35 kJ, provided the equations add to the target reaction.
การ์ด 287
คำถาม
Why is “bonds breaking releases energy” incorrect?
คำตอบ
Bond breaking absorbs energy; the overall reaction releases energy only when forming new bonds releases more than breaking old bonds requires.
การ์ด 288
คำถาม
How would melting appear on an energy diagram?
คำตอบ
The liquid lies above the solid, so ΔHfus is positive; the diagram represents a physical, endothermic change.
การ์ด 289
คำถาม
Can two objects at the same temperature exchange energy microscopically?
คำตอบ
Yes, but their energy transfers balance, so there is no net heat flow.
การ์ด 290
คำถาม
Why must the calorimeter's heat capacity be included when it isn't negligible?
คำตอบ
The apparatus can absorb or release heat, so include q_cal = C_calΔT in the energy balance: q_process + q_solution + q_cal = 0.
การ์ด 291
คำถาม
What makes chemical equilibrium dynamic?
คำตอบ
Forward and reverse reactions continue at equal rates even though macroscopic concentrations stay constant.
การ์ด 292
คำถาม
For aA + bB ⇌ cC, what is the concentration-form expression for Q?
คำตอบ
Q = [C]^c / ([A]^a[B]^b), using current rather than necessarily equilibrium concentrations.
การ์ด 293
คำถาม
What does K much greater than 1 indicate?
คำตอบ
Products predominate at equilibrium, though K says nothing about reaction speed.
การ์ด 294
คำถาม
How does reversing a reaction change its equilibrium constant?
คำตอบ
K becomes 1/K.
การ์ด 295
คำถาม
Can a reversible system reach equilibrium when it starts with only products?
คำตอบ
Yes, if the reverse reaction is possible. The equilibrium composition depends on temperature, initial amounts, and volume or pressure.
การ์ด 296
คำถาม
How do Q and K predict reaction direction?
คำตอบ
Q < K shifts forward, Q > K shifts reverse, and Q = K means equilibrium.
การ์ด 297
คำถาม
Which species are omitted from a heterogeneous equilibrium expression?
คำตอบ
Pure solids and pure liquids because their activities are effectively constant.
การ์ด 298
คำถาม
How does increasing a dissolved reactant's concentration or a gaseous reactant's partial pressure affect equilibrium at constant temperature when other Q terms are initially unchanged?
คำตอบ
It lowers Q relative to K, so the system shifts toward products until Q = K again. Changing the amount of a pure solid or liquid omitted from Q does not cause this shift while that pure phase remains present.
การ์ด 299
คำถาม
What does a flat concentration-time graph mean at equilibrium?
คำตอบ
Each concentration is constant, not necessarily equal to the others.
การ์ด 300
คำถาม
For A ⇌ B in one fixed volume, a particulate model shows 16 A and 0 B initially, then 4 A and 12 B at equilibrium. What changed, what predominates, and what is Kc?
คำตอบ
The net change was forward: 12 A particles became 12 B particles. B predominates at equilibrium, and Kc = [B]/[A] = 12/4 = 3.0 because both counts come from the same fixed volume.
การ์ด 301
คำถาม
What can Ksp tell you about a salt's solubility, and when can two Ksp values be compared directly?
คำตอบ
Ksp > 1 indicates a soluble salt. For salts with the same dissolution stoichiometry, a larger Ksp generally means greater molar solubility; across different stoichiometries, calculate molar solubility before comparing.
การ์ด 302
คำถาม
What is the common-ion effect on solubility?
คำตอบ
Adding an ion already in the dissolution equilibrium usually decreases the solid's molar solubility.
การ์ด 303
คำถาม
How does uniform dilution shift an aqueous equilibrium based on the stoichiometric powers in Q?
คำตอบ
It shifts toward the side with the larger sum of stoichiometric coefficients for dissolved species included in Q. If the sums are equal, dilution causes no shift by this effect; pure solids and liquids remain omitted.
การ์ด 304
คำถาม
What happens if a reversible reaction starts with reactants only?
คำตอบ
The forward rate is initially largest; products form, the reverse rate grows, and the rates eventually become equal.
การ์ด 305
คำถาม
What is the purpose of an ICE table?
คำตอบ
To organize initial, change, and equilibrium concentrations using reaction stoichiometry.
การ์ด 306
คำถาม
Can a reaction with a very large K be slow?
คำตอบ
Yes. K describes thermodynamic equilibrium position, while rate depends on kinetics and activation energy.
การ์ด 307
คำถาม
What happens to Q immediately after product concentration increases?
คำตอบ
Q increases; if it rises above K, the reaction shifts toward reactants.
การ์ด 308
คำถาม
How does multiplying every reaction coefficient by 2 affect K?
คำตอบ
The new equilibrium constant is K².
การ์ด 309
คำถาม
For A ⇌ B, Kc = 4.0 and initially [A] = 1.0 M and [B] = 0, what are the equilibrium concentrations?
คำตอบ
[A] = 0.20 M and [B] = 0.80 M. Let x form: Kc = x/(1.0 − x) = 4.0, so x = 0.80 M.
การ์ด 310
คำถาม
What macroscopic properties stay constant at equilibrium?
คำตอบ
Properties such as concentration, color, and pressure remain constant when external conditions are fixed.
การ์ด 311
คำถาม
How does decreasing volume shift a gaseous equilibrium?
คำตอบ
Toward the side with fewer moles of gas, if the two sides have different gaseous mole counts.
การ์ด 312
คำถาม
For N₂ + 3H₂ ⇌ 2NH₃, what is Kc?
คำตอบ
Kc = [NH₃]² / ([N₂][H₂]³).
การ์ด 313
คำถาม
For CaF₂(s) ⇌ Ca²⁺ + 2F⁻, how is Ksp written in terms of molar solubility s in pure water?
คำตอบ
Ksp = s(2s)² = 4s³ because [Ca²⁺] = s and [F⁻] = 2s.
การ์ด 314
คำถาม
What does K much less than 1 indicate?
คำตอบ
Reactants predominate at equilibrium.
การ์ด 315
คำถาม
How does decreasing a dissolved product's concentration or a gaseous product's partial pressure affect equilibrium when other Q terms are initially unchanged?
คำตอบ
It lowers Q and drives a net forward reaction until equilibrium returns. Changing the amount of a pure solid or liquid omitted from Q does not cause this shift while that phase remains.
การ์ด 316
คำถาม
Does equilibrium mean the reaction has stopped?
คำตอบ
No. Both directions continue, but equal rates produce no net macroscopic change.
การ์ด 317
คำถาม
Why does adding NaF reduce CaF₂ solubility?
คำตอบ
The added F⁻ raises Qsp, shifting the dissolution equilibrium toward solid CaF₂.
การ์ด 318
คำถาม
For N₂ + 3H₂ ⇌ 2NH₃, what is Kp when P_N₂ = 0.50 atm, P_H₂ = 1.50 atm, and P_NH₃ = 0.25 atm?
คำตอบ
0.037. Use Kp = (P_NH₃)²/[(P_N₂)(P_H₂)³] = (0.25)²/[(0.50)(1.50)³]. Use equilibrium partial pressures directly; Kc↔Kp conversion isn't assessed.
การ์ด 319
คำถาม
What happens to Q when a gaseous equilibrium mixture is compressed at constant temperature if products have fewer gas moles?
คำตอบ
Q falls relative to K, so the reaction shifts toward products.
การ์ด 320
คำถาม
How do K and Q transform when a reaction is reversed, its coefficients are multiplied, or reactions are added?
คำตอบ
They follow the same algebra: reversing takes the reciprocal, multiplying every coefficient by c raises the value to the power c, and adding reactions multiplies their K or Q values.
การ์ด 321
คำถาม
When is the small-x approximation acceptable?
คำตอบ
When x is small relative to the initial concentration and the final result confirms the neglected change is suitably small.
การ์ด 322
คำถาม
What graph feature shows a disturbance followed by re-equilibration?
คำตอบ
A sudden or gradual concentration change followed by new constant plateaus while rates return to equality.
การ์ด 323
คำถาม
If Q = 0.20 and K = 5.0, which direction is favored next?
คำตอบ
Forward, because Q < K.
การ์ด 324
คำถาม
At equilibrium, are reactant and product concentrations equal?
คำตอบ
Not necessarily. They are constant, while forward and reverse rates are equal.
การ์ด 325
คำถาม
CaF₂ has Ksp = 3.2 × 10^-11 in pure water; what is its molar solubility?
คำตอบ
2.0 × 10^-4 M. If the molar solubility is s, then [Ca²⁺] = s, [F⁻] = 2s, and Ksp = 4s³.
การ์ด 326
คำถาม
For N₂ + 3H₂ ⇌ 2NH₃, how is Qp written?
คำตอบ
Qp = (P_NH₃)²/[(P_N₂)(P_H₂)³], using the current partial pressures rather than necessarily equilibrium values.
การ์ด 327
คำถาม
How does heating shift an endothermic forward reaction?
คำตอบ
Toward products, and K increases because temperature changes the equilibrium constant.
การ์ด 328
คำถาม
Why do both forward and reverse rates change as equilibrium is approached?
คำตอบ
As reactant and product concentrations change, the collision frequencies for the two directions change until their rates match.
การ์ด 329
คำถาม
CaF₂ has Ksp = 3.2 × 10^-11. What is its molar solubility in 0.10 M NaF?
คำตอบ
About 3.2 × 10^-9 M. With [F⁻] ≈ 0.10 M, Ksp = [Ca²⁺][F⁻]² gives s = (3.2 × 10^-11)/(0.10)². The common ion lowers solubility but does not change Ksp at constant temperature.
การ์ด 330
คำถาม
What concentration data must be used to calculate Kc?
คำตอบ
Equilibrium concentrations, each raised to its stoichiometric coefficient and excluding pure solids and liquids.
การ์ด 331
คำถาม
What is a Brønsted–Lowry acid?
คำตอบ
A proton donor.
การ์ด 332
คำถาม
How is pH defined?
คำตอบ
pH = -log[H₃O⁺].
การ์ด 333
คำถาม
What is Ka for HA + H₂O ⇌ H₃O⁺ + A⁻?
คำตอบ
Ka = [H₃O⁺][A⁻]/[HA].
การ์ด 334
คำถาม
How does stabilizing a base affect its basicity and the strength of its conjugate acid?
คำตอบ
It makes the base weaker and its conjugate acid stronger. A more stable base is less willing to accept H⁺.
การ์ด 335
คำถาม
What is a Brønsted–Lowry base?
คำตอบ
A proton acceptor.
การ์ด 336
คำถาม
At 25°C, what are Kw and the relationship between pH and pOH?
คำตอบ
Kw = [H₃O⁺][OH⁻] = 1.0 × 10^-14. Taking negative logarithms gives pH + pOH = 14.00.
การ์ด 337
คำถาม
What is Kb for B + H₂O ⇌ BH⁺ + OH⁻?
คำตอบ
Kb = [BH⁺][OH⁻]/[B].
การ์ด 338
คำถาม
Why can lowering pH increase the solubility of a salt containing a basic anion?
คำตอบ
H₃O⁺ consumes the anion, pulling the dissolution equilibrium toward more dissolved ions.
การ์ด 339
คำถาม
What are conjugate acid–base pairs?
คำตอบ
Species that differ by exactly one proton.
การ์ด 340
คำถาม
What is the pH of 1.0 × 10^-3 M HCl?
คำตอบ
3.00, assuming complete dissociation and negligible water contribution.
การ์ด 341
คำถาม
How are pKa and pKb defined?
คำตอบ
pKa = -log Ka, and pKb = -log Kb.
การ์ด 342
คำถาม
Why does acid strength increase across a row of comparable hydrides?
คำตอบ
Increasing electronegativity stabilizes the conjugate base and polarizes the H–A bond.
การ์ด 343
คำถาม
What is an amphiprotic species?
คำตอบ
A species that can donate or accept a proton, such as HCO₃⁻.
การ์ด 344
คำถาม
What amounts remain after a limited amount of strong base partially neutralizes weak acid HA?
คำตอบ
Subtract the reacted moles from HA and form the same number of moles of A⁻. The result gives the remaining HA and formed A⁻ amounts before any equilibrium or buffer-pH calculation.
การ์ด 345
คำถาม
How are Ka, Kb, pKa, and pKb related for a conjugate pair at 25°C?
คำตอบ
KaKb = Kw = 1.0 × 10^-14, and pKa + pKb = pKw = 14.00.
การ์ด 346
คำถาม
When does pH have little effect on a salt's solubility?
คำตอบ
When neither dissolved ion reacts appreciably with H₃O⁺ or OH⁻.
การ์ด 347
คำถาม
How does H₂O act in HCl + H₂O → H₃O⁺ + Cl⁻ and in NH₃ + H₂O ⇌ NH₄⁺ + OH⁻?
คำตอบ
It acts as a base in the first reaction by accepting H⁺, and as an acid in the second by donating H⁺.
การ์ด 348
คำถาม
After mixing weak base B with strong acid, what controls the final solution in the three stoichiometric regimes?
คำตอบ
Excess B leaves a B/BH⁺ buffer; equimolar amounts leave BH⁺, so the solution is acidic; excess strong acid sets the pH from the remaining H₃O⁺.
การ์ด 349
คำถาม
What two components make a typical weak-acid buffer?
คำตอบ
A weak acid and a significant amount of its conjugate base.
การ์ด 350
คำถาม
What do the successive half-equivalence pH values approximate in a diprotic weak-acid titration?
คำตอบ
The first approximates pKa₁ and the second approximates pKa₂ because each conjugate pair has equal concentrations at its half-equivalence point.
การ์ด 351
คำถาม
Which acid is stronger, one with pKa 2 or pKa 5?
คำตอบ
The acid with pKa 2; lower pKa means larger Ka.
การ์ด 352
คำถาม
What is the Henderson–Hasselbalch equation?
คำตอบ
pH = pKa + log([A⁻]/[HA]).
การ์ด 353
คำถาม
Why are larger binary hydrides down a group often stronger acids?
คำตอบ
The H–A bond becomes weaker as the central atom grows, so proton release is easier.
การ์ด 354
คำถาม
What mainly determines buffer capacity?
คำตอบ
The concentrations of both members of the conjugate acid–base pair. Increasing both concentrations at a fixed ratio increases capacity without changing pH; capacity is best balanced for added acid and base when their concentrations are similar.
การ์ด 355
คำถาม
Why does acid increase CaCO₃ solubility?
คำตอบ
H₃O⁺ converts CO₃²⁻ to HCO₃⁻ or carbonic acid species, reducing free carbonate and driving more CaCO₃ to dissolve.
การ์ด 356
คำถาม
What does pH < pKa imply for a weak-acid pair?
คำตอบ
The protonated form HA predominates over A⁻.
การ์ด 357
คำถาม
What happens when stoichiometrically equal amounts of a monoprotic weak acid and strong base are mixed?
คำตอบ
The weak acid is consumed to its conjugate base; at equivalence, the solution isn't a buffer containing both forms.
การ์ด 358
คำถาม
What is [H₃O⁺] when pH = 4.50?
คำตอบ
3.2 × 10^-5 M, from [H₃O⁺] = 10^-pH.
การ์ด 359
คำถาม
What is the pH of 0.010 M Ba(OH)₂ at 25°C?
คำตอบ
About 12.30. Complete dissociation gives [OH⁻] = 0.020 M, so pOH = 1.70. At 25°C, pH + pOH = 14.00, so pH = 12.30.
การ์ด 360
คำถาม
How does a buffer respond to a small amount of added strong acid?
คำตอบ
Its conjugate base consumes H⁺, converting to the weak acid and limiting the pH change.
การ์ด 361
คำถาม
Why is the equivalence-point solution basic in a monoprotic weak-acid–strong-base titration?
คำตอบ
The conjugate base produced at equivalence reacts with water to form OH⁻, so the pH is above neutral—above 7.00 at 25°C.
การ์ด 362
คำถาม
How is percent ionization calculated for a weak acid or weak base?
คำตอบ
For HA, use ([H₃O⁺]equilibrium ÷ [HA]initial) × 100%. For B, use ([BH⁺]equilibrium ÷ [B]initial) × 100%, under the usual monoprotic setup.
การ์ด 363
คำถาม
When is Henderson–Hasselbalch useful for an initial buffer-pH calculation?
คำตอบ
Use it when both members of a conjugate acid–base pair are present in meaningful amounts, including after in-scope stoichiometry creates a buffer. Calculating the pH change after acid or base is added to an existing buffer is outside this deck’s scope.
การ์ด 364
คำถาม
Why does adding oxygen atoms usually strengthen oxyacids with the same central atom?
คำตอบ
Extra oxygens withdraw electron density and delocalize negative charge in the conjugate base.
การ์ด 365
คำถาม
A prepared buffer is accidentally diluted to twice its intended volume; what happens to its pH and capacity?
คำตอบ
Its pH stays nearly the same, and its capacity per liter is halved because both component concentrations halve. The total neutralizing moles in the sample remain unchanged.
การ์ด 366
คำถาม
How does adding OH⁻ affect Mg(OH)₂ solubility?
คำตอบ
It decreases solubility through the common-ion effect, shifting Mg(OH)₂(s) ⇌ Mg²⁺ + 2OH⁻ toward the solid.
การ์ด 367
คำถาม
A buffer has equal [A⁻] and [HA]; what is its pH?
คำตอบ
pH = pKa because log(1) = 0.
การ์ด 368
คำถาม
How should a weak acid–strong base mixture be solved before equivalence?
คำตอบ
First use mole stoichiometry; if both HA and A⁻ remain, use the resulting buffer relation.
การ์ด 369
คำถาม
Why can pure neutral water have a pH other than 7.00?
คำตอบ
Kw changes with temperature. Neutrality means [H₃O⁺] = [OH⁻], while pH = 7.00 only when Kw = 1.0 × 10^-14 at 25°C.
การ์ด 370
คำถาม
25.0 mL of 0.200 M HCl is diluted to 100.0 mL; what is the pH?
คำตอบ
1.301. Dilution gives [H₃O⁺] = (0.200 M)(25.0 mL)/(100.0 mL) = 0.0500 M, so pH = -log(0.0500).
การ์ด 371
คำถาม
How does a buffer respond to a small amount of added strong base?
คำตอบ
The weak acid consumes OH⁻, forming conjugate base and water.
การ์ด 372
คำถาม
How do you find the final pH after mixing a strong acid and strong base at 25°C?
คำตอบ
Use H₃O⁺ + OH⁻ → 2H₂O and compare their moles. Divide excess H₃O⁺ or OH⁻ by the total volume, then calculate pH or pOH from that excess concentration. Equal moles give pH 7.00 at 25°C.
การ์ด 373
คำถาม
What distinguishes acid strength from acid concentration?
คำตอบ
Strength is the equilibrium tendency to donate H⁺, reflected by Ka or pKa; concentration is the amount of acid per solution volume.
การ์ด 374
คำถาม
If [A⁻]/[HA] = 10, how does pH compare with pKa?
คำตอบ
pH = pKa + 1 because log 10 = 1.
การ์ด 375
คำถาม
Which conjugate base is more stable, one with localized or resonance-delocalized charge?
คำตอบ
The resonance-delocalized conjugate base, which generally corresponds to the stronger acid.
การ์ด 376
คำถาม
Which 1.0 L buffer has greater capacity: 1.0 mol each of HA/A⁻ or 0.10 mol each at the same ratio?
คำตอบ
The 1.0 mol pair; both have the same initial pH, but the larger amounts neutralize more added acid or base.
การ์ด 377
คำถาม
For BHX(s) ⇌ BH⁺ + X⁻, why can raising pH increase the salt's solubility?
คำตอบ
OH⁻ consumes BH⁺ to form B and H₂O, so dissolution shifts right to replace BH⁺. This is a qualitative prediction, not a pH-dependent solubility calculation.
การ์ด 378
คำถาม
What does pH > pKa imply for a weak-acid pair?
คำตอบ
The deprotonated form A⁻ predominates over HA.
การ์ด 379
คำถาม
For HA + B ⇌ A⁻ + BH⁺, which side is favored when pKa(HA) = 4 and pKa(BH⁺) = 9?
คำตอบ
Products are favored. Proton transfer moves toward the weaker acid–base pair, and K ≈ 10^(9 − 4) = 10^5.
การ์ด 380
คำถาม
What is the pOH when [OH⁻] = 2.5 × 10^-4 M?
คำตอบ
3.60, from -log(2.5 × 10^-4).
การ์ด 381
คำถาม
What is the pH of 0.100 M HA when Ka = 1.0 × 10^-5?
คำตอบ
About 3.00. The ICE setup gives Ka = x²/(0.100 − x); x ≈ 1.0 × 10^-3 M, and the 1.0% change validates the approximation.
การ์ด 382
คำถาม
Why does a buffer fail after too much strong acid is added?
คำตอบ
Its conjugate base is depleted, so added H⁺ is no longer consumed effectively.
การ์ด 383
คำถาม
What do two clear equivalence regions on an acid titration curve suggest?
คำตอบ
At least two distinguishable titratable protons; on a clean ideal curve with exactly two equivalence regions, this is consistent with a diprotic acid.
การ์ด 384
คำถาม
A buffer has pKa 4.8 and [A⁻]/[HA] = 0.10; what is pH?
คำตอบ
3.8, from 4.8 + log(0.10).
การ์ด 385
คำถาม
Why is HCl stronger than HF in water despite F being more electronegative?
คำตอบ
The H–F bond is much stronger; bond strength dominates this down-group binary-acid comparison.
การ์ด 386
คำถาม
Why does percent ionization increase when a weak acid is diluted?
คำตอบ
Dilution shifts ionization toward more particles, so a larger fraction ionizes even though [H₃O⁺] decreases.
การ์ด 387
คำถาม
A buffer contains more HA than A⁻. Which addition can it neutralize in greater amount: strong acid or strong base?
คำตอบ
Strong base. The larger HA reserve consumes more added OH⁻; a buffer with more A⁻ than HA instead has greater capacity for added strong acid.
การ์ด 388
คำถาม
Why can removing a basic anion increase a salt's molar solubility without changing Ksp?
คำตอบ
The equilibrium shifts to replace the consumed ion; Ksp remains fixed at the same temperature.
การ์ด 389
คำถาม
Why can an acid–base indicator change color as pH changes?
คำตอบ
Its protonated and deprotonated forms have different colors or other observable properties, and their relative amounts change with pH.
การ์ด 390
คำถาม
What buffer results from mixing 1.0 mol HA with 0.40 mol OH⁻?
คำตอบ
0.60 mol HA and 0.40 mol A⁻ remain, forming a buffer before any equilibrium calculation.
การ์ด 391
คำถาม
What is the pH of 0.200 M weak base B when Kb = 2.0 × 10^-5 at 25°C?
คำตอบ
About 11.30. The ICE setup gives Kb = x²/(0.200 − x); x ≈ 2.0 × 10^-3 M OH⁻, and the 1.0% change validates the approximation.
การ์ด 392
คำถาม
Why does a weak acid alone not make an effective buffer?
คำตอบ
It lacks a substantial conjugate-base reserve to consume added strong acid.
การ์ด 393
คำถาม
What controls pH after excess strong base passes equivalence?
คำตอบ
The concentration of excess OH⁻ after accounting for reaction stoichiometry and total volume.
การ์ด 394
คำถาม
How should an indicator be chosen for a titration?
คำตอบ
Its color-change range should fall within the steep pH change near the equivalence point.
การ์ด 395
คำถาม
How can a measured pH and known pKa give a conjugate-base/acid ratio?
คำตอบ
Rearrange Henderson–Hasselbalch: [A⁻]/[HA] = 10^(pH − pKa).
การ์ด 396
คำถาม
Can a weak base and its conjugate acid form a buffer?
คำตอบ
Yes, when both are present in significant amounts.
การ์ด 397
คำถาม
For equal-volume buffers with the same conjugate-base/acid ratio, how does adding the same amount of strong acid affect a more concentrated versus less concentrated buffer?
คำตอบ
The concentrated buffer changes pH less because it has greater capacity.
การ์ด 398
คำถาม
How does equivalence-point pH compare for strong acid–strong base, weak acid–strong base, and weak base–strong acid titrations at 25°C?
คำตอบ
Strong acid–strong base: pH 7.00. Weak acid–strong base: above 7.00 because the conjugate base reacts with water. Weak base–strong acid: below 7.00 because the conjugate acid reacts with water.
การ์ด 399
คำถาม
Why should mole ratios replace concentration ratios after mixing buffer solutions?
คำตอบ
Both components share the same final volume, so that volume cancels in [A⁻]/[HA].
การ์ด 400
คำถาม
How does adding a little strong acid change a buffer's conjugate-base and conjugate-acid amounts?
คำตอบ
The conjugate base decreases and its conjugate acid increases by the amount of strong acid consumed.
การ์ด 401
คำถาม
What does entropy measure qualitatively?
คำตอบ
The dispersal of matter and energy among available microstates.
การ์ด 402
คำถาม
How is standard reaction entropy calculated?
คำตอบ
ΔS°rxn = ΣνS°(products) − ΣνS°(reactants).
การ์ด 403
คำถาม
What equation gives ΔG° from ΔH° and ΔS°, and what standard states do the degree symbols assume?
คำตอบ
ΔG° = ΔH° − TΔS°. The standard states are pure substances, 1.0 M solutions, and gases at 1 atm or 1 bar; T is in kelvins and energy units must match.
การ์ด 404
คำถาม
Does thermodynamic favorability guarantee a fast reaction?
คำตอบ
No. A favorable reaction can be slow when its activation barrier is large.
การ์ด 405
คำถาม
What is ΔG at equilibrium?
คำตอบ
Zero under the current conditions because there is no net driving force.
การ์ด 406
คำถาม
Why can an endothermic dissolution still be thermodynamically favorable?
คำตอบ
A sufficiently positive entropy change can make TΔS exceed positive ΔH, giving negative ΔG.
การ์ด 407
คำถาม
How can an unfavorable reaction be driven by a favorable one?
คำตอบ
Couple them so their equations and ΔG values add to a negative overall ΔG.
การ์ด 408
คำถาม
Where does oxidation occur in every electrochemical cell?
คำตอบ
At the anode.
การ์ด 409
คำถาม
How are standard cell potential and standard free energy related?
คำตอบ
ΔG° = -nFE°cell.
การ์ด 410
คำถาม
What equation gives cell potential under nonstandard conditions?
คำตอบ
E = E° − (RT/nF) ln Q. When Q = 1, ln Q = 0, so E = E°.
การ์ด 411
คำถาม
How is electrical charge related to current and time?
คำตอบ
q = It.
การ์ด 412
คำถาม
Which phase has greater molar entropy, liquid water or ice at the same temperature?
คำตอบ
Liquid water because its molecules have more accessible arrangements and motion.
การ์ด 413
คำถาม
Do elements in their standard states have zero standard molar entropy?
คำตอบ
No. Their ΔHf° is zero, but their absolute S° values are positive above 0 K.
การ์ด 414
คำถาม
How do the four ΔH° and ΔS° sign combinations determine thermodynamic favorability across temperature?
คำตอบ
ΔH° < 0 and ΔS° > 0 is favorable at every temperature; ΔH° > 0 and ΔS° < 0 is thermodynamically unfavored at every temperature. If both are positive, favorability requires high temperature; if both are negative, it requires low temperature.
การ์ด 415
คำถาม
What does it indicate when a thermodynamically favored process does not occur at a measurable rate?
คำตอบ
It is under kinetic control, commonly because of a high activation energy; no measurable reaction does not mean the system is at equilibrium.
การ์ด 416
คำถาม
How are ΔG° and K related?
คำตอบ
ΔG° = -RT ln K.
การ์ด 417
คำถาม
What two contributions compete in dissolving an ionic solid?
คำตอบ
Enthalpy changes from separating and solvating particles, and entropy changes from their new dispersal and solvent organization.
การ์ด 418
คำถาม
What must cancel when coupled reactions are added?
คำตอบ
Shared intermediates, leaving the desired net reaction.
การ์ด 419
คำถาม
Where does reduction occur in every electrochemical cell?
คำตอบ
At the cathode.
การ์ด 420
คำถาม
What sign of E°cell indicates a favorable standard galvanic reaction?
คำตอบ
Positive E°cell, corresponding to negative ΔG°.
การ์ด 421
คำถาม
If Q increases for a galvanic reaction, how does E change at fixed temperature?
คำตอบ
E decreases according to the Nernst equation. Le Châtelier's principle does not apply to an operating cell away from equilibrium; use Q and Nernst reasoning instead.
การ์ด 422
คำถาม
How are moles of electrons found from charge?
คำตอบ
Moles e⁻ = q/F, where F ≈ 96485 C mol^-1 e⁻.
การ์ด 423
คำถาม
How does producing more gas particles usually affect system entropy?
คำตอบ
It increases entropy because the particles have more positional microstates.
การ์ด 424
คำถาม
Can a dissolution with negative ΔH be unfavorable?
คำตอบ
Yes. A sufficiently negative entropy change at the stated temperature can make ΔG positive.
การ์ด 425
คำถาม
When can a process with ΔH > 0 and ΔS > 0 become favorable?
คำตอบ
At sufficiently high temperature, when TΔS exceeds ΔH.
การ์ด 426
คำถาม
How does a catalyst affect ΔG?
คำตอบ
It does not change ΔG; it lowers the activation barrier for both directions.
การ์ด 427
คำถาม
For A → B, ΔGf°(A) = -50 kJ mol^-1 and ΔGf°(B) = -80 kJ mol^-1. What is ΔG°rxn?
คำตอบ
-30 kJ mol^-1. Use ΣνΔGf°(products) − ΣνΔGf°(reactants) = -80 − (-50).
การ์ด 428
คำถาม
Why can dissolving a gas in a liquid have a negative entropy change?
คำตอบ
Gas particles lose much of their translational freedom when confined and solvated in the liquid.
การ์ด 429
คำถาม
If coupled steps have ΔG values +20 kJ and -35 kJ, what is overall ΔG?
คำตอบ
-15 kJ, so the combined process is thermodynamically favorable under those conditions.
การ์ด 430
คำถาม
What role does each half-cell solution play in an electrochemical cell?
คำตอบ
It supplies dissolved redox species at an electrode interface and carries ions within its compartment. Separate compartments prevent direct mixing while the external circuit and salt bridge connect the half-cells.
การ์ด 431
คำถาม
How is E°cell found from standard reduction potentials?
คำตอบ
E°cell = E°cathode − E°anode, using both tabulated values as reductions.
การ์ด 432
คำถาม
How does a cell's potential magnitude change as Q approaches or moves away from K, and what is E at equilibrium?
คำตอบ
|E| falls toward zero as Q approaches K and grows as the system moves farther from equilibrium. At equilibrium, Q = K and E = 0.
การ์ด 433
คำถาม
How many moles of electrons pass when 1.93 × 10^5 C flows?
คำตอบ
2.00 mol e⁻, from q/F.
การ์ด 434
คำถาม
How does a salt bridge maintain charge balance in a galvanic cell?
คำตอบ
Anions migrate toward the anode compartment and cations toward the cathode compartment, countering the net charge imbalances created by the two half-reactions.
การ์ด 435
คำถาม
Why does raising a substance's temperature generally increase its entropy?
คำตอบ
Energy spreads across more accessible particle energy states, increasing the number of possible microscopic arrangements.
การ์ด 436
คำถาม
When can a process with ΔH < 0 and ΔS < 0 be favorable?
คำตอบ
At sufficiently low temperature, where the unfavorable -TΔS term is small.
การ์ด 437
คำถาม
Why can diamond persist even though graphite is more stable at standard conditions?
คำตอบ
Conversion has a large activation barrier, so diamond is kinetically persistent.
การ์ด 438
คำถาม
What do the external circuit and measuring device do in an electrochemical cell?
คำตอบ
The circuit carries electrons from anode to cathode; a voltmeter measures potential difference, while an ammeter in series measures current.
การ์ด 439
คำถาม
At constant temperature, how does increasing the volume available to a gas affect its entropy?
คำตอบ
Entropy increases because the gas particles can occupy more positions in the larger space, so more microstates are accessible.
การ์ด 440
คำถาม
How does reversing one coupled reaction affect its ΔG?
คำตอบ
It reverses the sign of that reaction's ΔG.
การ์ด 441
คำถาม
Why is n required in ΔG° = -nFE°?
คำตอบ
It is the moles of electrons transferred per balanced reaction, linking charge flow to reaction extent.
การ์ด 442
คำถาม
What makes an electrolytic cell operate?
คำตอบ
An external power source drives a thermodynamically unfavorable redox reaction; oxidation still occurs at the anode and reduction at the cathode.
การ์ด 443
คำถาม
In an Mⁿ⁺/M concentration cell, which half-cell is the anode: the dilute or concentrated ion solution?
คำตอบ
The dilute half-cell. Oxidation produces Mⁿ⁺ there, while reduction consumes Mⁿ⁺ in the concentrated half-cell, so electrons flow from dilute to concentrated as the concentrations move toward equality.
การ์ด 444
คำถาม
How is deposited metal mass found from current and time?
คำตอบ
Find q = It, convert q/F to moles e⁻, use the half-reaction ratio to moles metal, then multiply by molar mass.
การ์ด 445
คำถาม
Given product S° total 500 J mol^-1 K^-1 and reactant total 420 J mol^-1 K^-1, what is ΔS°?
คำตอบ
+80 J mol^-1 K^-1.
การ์ด 446
คำถาม
How do electrode masses change in a Zn–Cu galvanic cell?
คำตอบ
The Zn anode loses mass as Zn → Zn²⁺ + 2e⁻, while the Cu cathode gains mass as Cu²⁺ + 2e⁻ → Cu.
การ์ด 447
คำถาม
What is ΔG° when ΔH° = 50 kJ mol^-1, ΔS° = 0.200 kJ mol^-1 K^-1, and T = 300 K?
คำตอบ
-10 kJ mol^-1, from ΔG° = 50 − (300)(0.200).
การ์ด 448
คำถาม
Why can temperature change a solid's solubility?
คำตอบ
Temperature changes the balance of ΔH and TΔS, so it changes the free energy of dissolution and the equilibrium constant.
การ์ด 449
คำถาม
What does the size of ΔG° relative to RT imply about K?
คำตอบ
ΔG° near zero gives K near 1. When |ΔG°| is much larger than RT, K is far from 1: negative ΔG° gives K ≫ 1, while positive ΔG° gives K ≪ 1.
การ์ด 450
คำถาม
Bubbles form at an inert cathode in acidic solution; which half-reaction can explain them?
คำตอบ
2H⁺ + 2e⁻ → H₂(g). Gas evolution at the cathode can be direct evidence of reduction.
450 การ์ด
AP Chemistry Flashcards: Complete 9-Unit Course Review
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