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