AP Chemistry Practice Test 7
60 original exam-style multiple-choice questions with answers & explanations — covering all nine units of the AP Chemistry course.
Note: These are original practice questions written in the AP Chemistry exam style — not reproduced College Board questions. Use them to test your readiness for the real AP Chemistry exam.
📱 How to use: Try each question first, then click “Show Answer” to check. Covers all 9 AP units: atomic structure, compound structure, intermolecular forces, reactions, kinetics, thermodynamics, equilibrium, acids & bases, and applications of thermodynamics.
⚛ Unit 1: Atomic Structure & Properties
Q1Naturally occurring boron consists of two isotopes: ^10B (mass 10.01 u, 19.9% abundance) and ^11B (mass 11.01 u, 80.1% abundance). The average atomic mass of boron is closest to
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Correct: (B)
0.199(10.01) + 0.801(11.01) = 1.99 + 8.82 = 10.81 u.
Q2What is the ground-state electron configuration of the Fe^3+ ion?
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Correct: (C)
Fe is [Ar]4s^2 3d^6; Fe^3+ loses both 4s electrons first and then one 3d electron, giving [Ar]3d^5.
Q3The photoelectron spectrum of an element shows three peaks. The peak at the highest binding energy has a relative height of 2, and each of the two peaks at lower binding energy also has a relative height of 2. The element is
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Correct: (A)
The peaks correspond to 1s (2 electrons), 2s (2), and 2p (2), a total of 6 electrons, which is carbon. Nitrogen would show a 2p peak of height 3 and boron a height of 1.
Q4Which of the following elements has the largest atomic radius?
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Correct: (D)
Atomic radius increases down a group; Ba is the lowest member of group 2 listed, so it has the largest radius.
Q5A mass spectrum of an element X shows peaks at m/z 63 (69.2% relative abundance) and m/z 65 (30.8% relative abundance). The average atomic mass of X is closest to
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Correct: (B)
0.692(63) + 0.308(65) = 43.6 + 20.0 = 63.6 u (the element is copper).
Q6Which of the following elements has the highest first ionization energy?
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Correct: (A)
First ionization energy generally increases across a period; P is the farthest right of these period 3 elements.
Q7The ground-state electron configuration of a chromium atom is
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Correct: (C)
Chromium is an exception to the expected filling order; the half-filled 3d subshell gives [Ar]4s^1 3d^5.
🔗 Unit 2: Molecular & Ionic Compound Structure
Q8In the best Lewis structure of CO2, O=C=O, the formal charges on the carbon atom and on each oxygen atom are
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Correct: (D)
With two double bonds, every atom has a complete octet and a formal charge of zero.
Q9How many equivalent resonance structures can be drawn for the nitrate ion, NO3^-?
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Correct: (B)
The double bond can be placed on any one of the three equivalent oxygen atoms, giving 3 resonance structures.
Q10In a Lewis structure of SO4^2- that minimizes formal charges (expanded octet on sulfur, with two S=O double bonds and two S-O single bonds), the formal charge on sulfur is
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Correct: (A)
Formal charge = 6 – (0 nonbonding electrons + 12 bonding electrons/2) = 6 – 6 = 0.
Q11The molecular geometry of SF4 is
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Correct: (C)
SF4 has 5 electron domains (4 bonds, 1 lone pair) in a trigonal bipyramidal arrangement; the lone pair occupies an equatorial position, giving a seesaw shape.
Q12The hybridization of the carbon atom in formaldehyde, CH2O, is
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Correct: (B)
Carbon has three electron domains (two C-H bonds and one C=O double bond), so it is sp^2 hybridized.
Q13Which of the following compounds has the largest lattice energy?
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Correct: (D)
Lattice energy increases with ionic charge; Mg^2+ and O^2- have charges of +2 and -2, much larger in magnitude than the +1/-1 ions in the other choices.
Q14The bond order of the bond in an N2 molecule is
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Correct: (A)
N2 has a triple bond (one sigma and two pi bonds), so the bond order is 3.
💧 Unit 3: Intermolecular Forces & Properties
Q15Which of the following substances has the highest boiling point?
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Correct: (C)
HF molecules form hydrogen bonds, an especially strong intermolecular force, so HF boils much higher than the other hydrogen halides despite its low molar mass.
Q16Which of the following compounds is most soluble in water?
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Correct: (A)
Methanol is polar and hydrogen bonds with water, making it fully miscible; the other choices are nonpolar.
Q17How much heat is required to melt 36.0 g of ice at 0°C? (ΔHfus of ice = 6.01 kJ/mol)
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Correct: (D)
36.0 g / 18.0 g/mol = 2.00 mol; q = 2.00 mol × 6.01 kJ/mol = 12.0 kJ.
Q18Silicon dioxide, SiO2, is best classified as a
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Correct: (B)
Each Si atom is covalently bonded to four O atoms in a continuous three-dimensional network, making SiO2 a network covalent solid.
Q19At 25°C, which of the following liquids has the highest vapor pressure?
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Correct: (C)
Diethyl ether has only weak dipole and dispersion forces, so its molecules escape into the gas phase most easily, giving the highest vapor pressure.
Q20What is the molality of a solution prepared by dissolving 0.50 mol of NaCl in 500 g of water?
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Correct: (A)
Molality = 0.50 mol / 0.500 kg = 1.0 m.
⚖ Unit 4: Chemical Reactions
Q21When the equation C3H8 + O2 → CO2 + H2O is balanced with the smallest whole-number coefficients, the coefficient of O2 is
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Correct: (B)
C3H8 + 5 O2 → 3 CO2 + 4 H2O.
Q22The oxidation number of sulfur in H2SO4 is
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Correct: (D)
With H at +1 (total +2) and O at -2 (total -8), sulfur must be +6 for the neutral compound to sum to zero.
Q23A solution of AgNO3 is mixed with a solution of NaCl and a precipitate forms. The net ionic equation for the reaction is
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Correct: (A)
Only Ag^+ and Cl^- combine to form the insoluble AgCl; Na^+ and NO3^- are spectator ions.
Q24For the reaction 2 H2(g) + O2(g) → 2 H2O(l), what mass of O2 is required to react completely with 8.0 g of H2?
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Correct: (C)
8.0 g H2 = 4.0 mol H2, which requires 2.0 mol O2 = 2.0 × 32.0 = 64 g.
Q25A mixture of 1.0 mol N2 and 2.0 mol H2 reacts according to N2 + 3 H2 → 2 NH3. The limiting reactant and the amount of NH3 formed are
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Correct: (B)
1.0 mol N2 would require 3.0 mol H2, but only 2.0 mol H2 is available, so H2 limits; NH3 formed = 2.0 mol H2 × (2/3) = 1.3 mol.
Q26A reaction has a theoretical yield of 50.0 g. If 42.5 g of product is actually obtained, the percent yield is
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Correct: (D)
Percent yield = (42.5 / 50.0) × 100% = 85.0%.
Q27A 25.0 mL sample of HCl(aq) is titrated with 0.100 M NaOH. If 30.0 mL of the NaOH is required to reach the equivalence point, the concentration of the HCl is
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Correct: (A)
mol NaOH = 0.100 × 0.0300 = 0.00300 mol = mol HCl; [HCl] = 0.00300 / 0.0250 = 0.120 M.
⏱ Unit 5: Kinetics
Q28For the reaction A + B → products, initial-rate experiments show that doubling [A] doubles the rate, while doubling [B] with [A] held constant increases the rate by a factor of 4. The rate law is
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Correct: (C)
Doubling [A] doubles the rate (first order in A); doubling [B] quadruples the rate (second order in B).
Q29A first-order reaction has a half-life of 20 min. The value of the rate constant k is
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Correct: (A)
k = 0.693 / t1/2 = 0.693 / 20 = 0.035 min^-1.
Q30For a reaction that is second order overall, the units of the rate constant k are
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Correct: (D)
Rate has units of M/s; for rate = k[A]^2, k must have units of M^-1 s^-1.
Q31A proposed mechanism for a reaction is: Step 1: A + B → C (slow); Step 2: C + B → D (fast). In this mechanism, species C is best described as
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Correct: (B)
C is formed in step 1 and consumed in step 2, which is the definition of an intermediate.
Q32A catalyst increases the rate of a reaction by
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Correct: (C)
A catalyst provides a different mechanism with a lower activation energy; it does not change ΔH or the equilibrium position.
Q33A first-order reaction has k = 0.050 s^-1. If the initial concentration of the reactant is 0.80 M, its concentration after 14 s is closest to
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Correct: (D)
The half-life is 0.693 / 0.050 = 14 s, so after 14 s the concentration has fallen by half, to 0.40 M.
Q34Raising the temperature of a reaction mixture increases the reaction rate mainly because
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Correct: (A)
At higher temperature the distribution of molecular energies shifts, so a much larger fraction of collisions can overcome the activation energy barrier.
🔥 Unit 6: Thermodynamics
Q35How much heat is absorbed when 100 g of water is heated from 20.0°C to 25.0°C? (specific heat of water = 4.184 J/g·°C)
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Correct: (B)
q = mcΔT = (100)(4.184)(5.0) = 2,092 J, approximately 2,090 J.
Q36Given: C(s) + O2(g) → CO2(g), ΔH = -393.5 kJ; and CO(g) + 1/2 O2(g) → CO2(g), ΔH = -283.0 kJ. The ΔH for the reaction C(s) + 1/2 O2(g) → CO(g) is
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Correct: (C)
By Hess's law, subtract the second reaction from the first: -393.5 – (-283.0) = -110.5 kJ.
Q37Using average bond enthalpies (H-H = 436 kJ/mol, Cl-Cl = 242 kJ/mol, H-Cl = 431 kJ/mol), the estimated ΔH for H2(g) + Cl2(g) → 2 HCl(g) is
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Correct: (A)
Bonds broken: 436 + 242 = 678 kJ; bonds formed: 2(431) = 862 kJ; ΔH = 678 – 862 = -184 kJ.
Q38Given standard enthalpies of formation (kJ/mol): CH4(g) = -74.8, CO2(g) = -393.5, H2O(l) = -285.8. The ΔH° for the combustion reaction CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l) is
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Correct: (D)
ΔH = [(-393.5) + 2(-285.8)] – [(-74.8) + 0] = -965.1 + 74.8 = -890.3 kJ.
Q39Which of the following processes results in an increase in the entropy of the system?
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Correct: (B)
Converting a liquid to a gas greatly increases the number of accessible microstates; the other processes all decrease entropy.
Q40A 50.0 g sample of an unknown metal at 100.0°C is placed in 100 g of water at 25.0°C. The final equilibrium temperature is 28.0°C. The specific heat of the metal is closest to (specific heat of water = 4.184 J/g·°C)
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Correct: (C)
Heat gained by water = (100)(4.184)(3.0) = 1,255 J. Then c = 1,255 / [(50.0)(100.0 – 28.0)] = 1,255 / 3,600 = 0.35 J/g·°C.
Q41The melting of ice, H2O(s) → H2O(l), is a process for which
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Correct: (A)
Melting requires an input of heat to break hydrogen bonds, so ΔH is positive even though the temperature stays constant.
⇆ Unit 7: Equilibrium
Q42For the equilibrium N2(g) + 3 H2(g) ⇌ 2 NH3(g), the equilibrium constant expression Kc is
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Correct: (D)
Kc is the product concentrations raised to their coefficients divided by the reactant concentrations raised to their coefficients.
Q43For the reaction H2(g) + I2(g) ⇌ 2 HI(g), Kc = 54 at a certain temperature. A flask initially contains 1.0 M H2 and 1.0 M I2 and no HI. The equilibrium concentration of HI is closest to
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Correct: (B)
Setting (2x)^2 / (1.0 – x)^2 = 54 gives 2x / (1.0 – x) = 7.35, so x = 0.79 and [HI] = 2x = 1.6 M.
Q44The reaction 2 SO2(g) + O2(g) ⇌ 2 SO3(g) is exothermic. Increasing the temperature of the equilibrium mixture will
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Correct: (C)
Heat can be treated as a product of an exothermic reaction; adding heat shifts the equilibrium toward reactants and decreases Kc.
Q45The Ksp of AgCl is 1.8 × 10^-10. The molar solubility of AgCl in pure water is
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Correct: (A)
For AgCl, Ksp = s^2, so s = sqrt(1.8 × 10^-10) = 1.3 × 10^-5 M.
Q46A reaction mixture is prepared for a reaction that has equilibrium constant K. Analysis shows that the reaction quotient Q is greater than K. Which statement is correct?
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Correct: (D)
When Q > K there are too many products relative to equilibrium, so the net reaction proceeds in reverse until Q = K.
Q47The Ksp of CaF2 is 3.9 × 10^-11. The molar solubility of CaF2 in a 0.10 M NaF solution is closest to
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Correct: (B)
With [F^-] fixed at approximately 0.10 M by the common ion, Ksp = s(0.10)^2, so s = 3.9 × 10^-11 / 0.010 = 3.9 × 10^-9 M.
Q48For the reaction N2(g) + 3 H2(g) ⇌ 2 NH3(g) at 500 K, Kc = 2.0. The value of Kp is closest to (R = 0.0821 L·atm/mol·K)
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Correct: (C)
Δn(gas) = 2 – 4 = -2, so Kp = Kc(RT)^-2 = 2.0 / (0.0821 × 500)^2 = 2.0 / (41.05)^2 = 1.2 × 10^-3.
🧫 Unit 8: Acids & Bases
Q49The pH of a 0.010 M HCl solution is
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Correct: (A)
HCl is a strong acid, so [H^+] = 0.010 M and pH = -log(0.010) = 2.00.
Q50The pH of a 0.10 M solution of acetic acid (Ka = 1.8 × 10^-5) is closest to
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Correct: (D)
[H^+] = sqrt(Ka × C) = sqrt(0.10 × 1.8 × 10^-5) = 1.3 × 10^-3 M, so pH = 2.87.
Q51A buffer solution contains 0.20 M acetic acid (pKa = 4.74) and 0.10 M sodium acetate. The pH of the buffer is
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Correct: (B)
pH = pKa + log([A^-]/[HA]) = 4.74 + log(0.10/0.20) = 4.74 – 0.30 = 4.44.
Q52A weak acid is titrated with a strong base. The pH at the equivalence point is
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Correct: (C)
At the equivalence point the solution contains the conjugate base of the weak acid, which hydrolyzes to produce OH^-, so the pH is above 7.
Q53The conjugate base of H2PO4^- is
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Correct: (A)
Removing one proton from H2PO4^- gives HPO4^2-, its conjugate base.
Q54The Ka of the ammonium ion, NH4^+, is 5.6 × 10^-10. The Kb of ammonia, NH3, is
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Correct: (D)
For a conjugate acid-base pair, Ka × Kb = Kw, so Kb = 1.0 × 10^-14 / 5.6 × 10^-10 = 1.8 × 10^-5.
🔋 Unit 9: Applications of Thermodynamics
Q55A reaction has ΔH = -100 kJ/mol and ΔS = -0.200 kJ/mol·K. At 298 K, ΔG for the reaction is
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Correct: (B)
ΔG = ΔH – TΔS = -100 – (298)(-0.200) = -100 + 59.6 = -40.4 kJ/mol, so the reaction is spontaneous at 298 K.
Q56A galvanic cell has E°cell = +1.10 V and transfers 2 mol of electrons per mole of reaction. The value of ΔG° for the reaction is closest to (F = 96,485 C/mol)
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Correct: (C)
ΔG° = -nFE° = -(2)(96,485)(1.10) = -212,000 J/mol = -212 kJ/mol.
Q57A standard galvanic cell is constructed with a Zn(s)/Zn^2+(aq) electrode and a Cu^2+(aq)/Cu(s) electrode. Given E°(Zn^2+/Zn) = -0.76 V and E°(Cu^2+/Cu) = +0.34 V, the standard cell potential is
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Correct: (A)
E°cell = E°(reduction) – E°(oxidation) = 0.34 – (-0.76) = +1.10 V.
Q58Copper is deposited by passing a current of 2.00 A through a CuSO4 solution for 30.0 min. The mass of Cu deposited is closest to (F = 96,485 C/mol; molar mass of Cu = 63.55 g/mol)
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Correct: (D)
Charge = 2.00 × 1,800 = 3,600 C = 0.0373 mol e^-. Since Cu^2+ + 2 e^- → Cu, mol Cu = 0.0187, and mass = 0.0187 × 63.55 = 1.19 g.
Q59For a process with ΔH = -90 kJ and ΔS = -0.30 kJ/K, the temperature at which ΔG = 0 is
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Correct: (B)
At ΔG = 0, T = ΔH/ΔS = (-90)/(-0.30) = 300 K. Below this temperature the process is spontaneous; above it, it is not.
Q60Which of the following reactions is expected to have ΔS < 0 for the system?
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Correct: (C)
The reaction converts 2 mol of gas into 1 mol of gas, decreasing the disorder of the system; the other reactions all produce more moles of gas than they consume.
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