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