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