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