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