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