Free AP Chemistry Practice Exam (PDF)

This free AP Chemistry practice exam covers all nine units at the depth the real exam expects: ionization-energy patterns, molecular polarity, limiting reagents, rate laws from trial data, Hess's law, calorimetry, Q versus K reasoning, Le Chatelier shifts, Ksp, weak-acid pH and electrochemistry. The long free-response question walks through a weak-acid titration at every stage: initial pH, half-equivalence buffer, equivalence-point hydrolysis and indicator choice, which is where students most often lose marks by assuming pH 7. All constants needed are given in the questions.

1. Question 11 mark · Atomic structure and periodicity
   The first four ionization energies of an element, in kJ/mol, are 738, 1451, 7733 and 10 540. The element is most likely:
   • A.
     Na
   • B.
     Mg
   • C.
     Al
   • D.
     Si
2. Question 21 mark · Electrochemistry
   Standard reduction potentials: $\mathrm{Ag^+ + e^- \rightarrow Ag}$, $E^{\circ} = +0.80$ V; $\mathrm{Cu^{2+} + 2e^- \rightarrow Cu}$, $+0.34$ V; $\mathrm{Fe^{2+} + 2e^- \rightarrow Fe}$, $-0.44$ V; $\mathrm{Zn^{2+} + 2e^- \rightarrow Zn}$, $-0.76$ V. Which species is the strongest reducing agent?
   • A.
     $\mathrm{Ag^+(aq)}$
   • B.
     $\mathrm{Ag(s)}$
   • C.
     $\mathrm{Zn^{2+}(aq)}$
   • D.
     $\mathrm{Zn(s)}$
3. Question 31 mark · Bonding and IMFs
   Which of the following molecules contains polar bonds but has no net dipole moment?
   • A.
     $\mathrm{SF_4}$
   • B.
     $\mathrm{XeF_4}$
   • C.
     $\mathrm{NH_3}$
   • D.
     $\mathrm{H_2O}$
4. Question 41 mark · Bonding and IMFs
   Propane ($\mathrm{CH_3CH_2CH_3}$, molar mass 44 g/mol), dimethyl ether ($\mathrm{CH_3OCH_3}$, 46 g/mol) and ethanol ($\mathrm{CH_3CH_2OH}$, 46 g/mol) have similar molar masses. Which has the highest boiling point, and why?
   • A.
     Propane, because it has the most hydrogen atoms
   • B.
     Dimethyl ether, because its oxygen atom gives it the strongest dipole-dipole forces
   • C.
     Ethanol, because its O-H bond allows hydrogen bonding between molecules
   • D.
     Ethanol and dimethyl ether boil at the same temperature, because they have the same molar mass
5. Question 51 mark · Stoichiometry
   Aluminum reacts with chlorine: $\mathrm{2Al + 3Cl_2 \rightarrow 2AlCl_3}$. If 4.0 mol of Al is mixed with 4.5 mol of $\mathrm{Cl_2}$, what is the maximum amount of $\mathrm{AlCl_3}$ that can form?
   • A.
     3.0 mol
   • B.
     4.0 mol
   • C.
     4.5 mol
   • D.
     6.0 mol
6. Question 61 mark · Gases
   An unknown gas has a density of 1.25 g/L at $0^{\circ}\text{C}$ and 1.00 atm, where the molar volume of an ideal gas is 22.4 L/mol. Molar masses: He 4.0, $\mathrm{N_2}$ 28.0, $\mathrm{O_2}$ 32.0, $\mathrm{CO_2}$ 44.0 g/mol. The gas is most likely:
   • A.
     He
   • B.
     $\mathrm{N_2}$
   • C.
     $\mathrm{O_2}$
   • D.
     $\mathrm{CO_2}$
7. Question 71 mark · Solutions
   A 25.0 mL sample of 0.40 M $\mathrm{CaCl_2}$ is diluted with water to a final volume of 100.0 mL. What is the concentration of chloride ions in the resulting solution?
   • A.
     0.10 M
   • B.
     0.20 M
   • C.
     0.40 M
   • D.
     0.80 M
8. Question 81 mark · Kinetics
   For the reaction $\mathrm{A + B \rightarrow products}$, three trials were run. Trial 1: $[\mathrm{A}] = 0.10$ M, $[\mathrm{B}] = 0.10$ M, initial rate $2.0 \times 10^{-4}$ M/s. Trial 2: $[\mathrm{A}] = 0.20$ M, $[\mathrm{B}] = 0.10$ M, rate $8.0 \times 10^{-4}$ M/s. Trial 3: $[\mathrm{A}] = 0.10$ M, $[\mathrm{B}] = 0.20$ M, rate $4.0 \times 10^{-4}$ M/s. What is the rate law?
   • A.
     rate $= k[\mathrm{A}][\mathrm{B}]$
   • B.
     rate $= k[\mathrm{A}]^2[\mathrm{B}]$
   • C.
     rate $= k[\mathrm{A}][\mathrm{B}]^2$
   • D.
     rate $= k[\mathrm{A}]^2[\mathrm{B}]^2$
9. Question 91 mark · Kinetics
   A compound X decomposes by a first-order reaction with a half-life of 20.0 min. If the initial concentration of X is 0.80 M, what is its concentration after 60.0 min?
   • A.
     0.40 M
   • B.
     0.27 M
   • C.
     0.20 M
   • D.
     0.10 M
10. Question 101 mark · Thermochemistry
    Given $\mathrm{C(s) + O_2(g) \rightarrow CO_2(g)}$, $\Delta H^{\circ} = -394$ kJ/mol, and $\mathrm{CO(g) + \tfrac{1}{2}O_2(g) \rightarrow CO_2(g)}$, $\Delta H^{\circ} = -283$ kJ/mol, what is $\Delta H^{\circ}$ for $\mathrm{C(s) + \tfrac{1}{2}O_2(g) \rightarrow CO(g)}$?
    • A.
      $-677$ kJ/mol
    • B.
      $-283$ kJ/mol
    • C.
      $-111$ kJ/mol
    • D.
      $+111$ kJ/mol
11. Question 111 mark · Thermochemistry
    A 50.0 g sample of water at $25.0^{\circ}\text{C}$ absorbs 2.09 kJ of heat. The specific heat capacity of water is $4.18\ \text{J g}^{-1}\,{}^{\circ}\text{C}^{-1}$. What is the final temperature of the water?
    • A.
      $27.5^{\circ}\text{C}$
    • B.
      $30.0^{\circ}\text{C}$
    • C.
      $35.0^{\circ}\text{C}$
    • D.
      $45.0^{\circ}\text{C}$
12. Question 121 mark · Equilibrium
    For $\mathrm{N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$, $K_c = 0.50$ at a certain temperature. A vessel at that temperature contains $[\mathrm{N_2}] = 2.0$ M, $[\mathrm{H_2}] = 1.0$ M and $[\mathrm{NH_3}] = 2.0$ M. Which statement is correct?
    • A.
      $Q = 2.0 > K_c$, so the reaction proceeds toward the reactants
    • B.
      $Q = 2.0 > K_c$, so the reaction proceeds toward the products
    • C.
      $Q = 0.50 = K_c$, so the system is at equilibrium
    • D.
      $Q = 0.25 < K_c$, so the reaction proceeds toward the products
13. Question 131 mark · Equilibrium
    The reaction $\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$ has $\Delta H^{\circ} = +57$ kJ/mol. A sealed cylinder fitted with a piston holds the system at equilibrium. Which change increases the equilibrium amount of $\mathrm{NO_2}$?
    • A.
      Increasing the temperature
    • B.
      Pushing the piston in to decrease the volume at constant temperature
    • C.
      Adding argon gas at constant volume and temperature
    • D.
      Adding a catalyst
14. Question 141 mark · Equilibrium
    A sparingly soluble salt dissolves as $\mathrm{M_2X(s) \rightleftharpoons 2M^+(aq) + X^{2-}(aq)}$ with $K_{sp} = 3.2 \times 10^{-11}$. What is the molar solubility of $\mathrm{M_2X}$ in pure water?
    • A.
      $5.7 \times 10^{-6}$ M
    • B.
      $2.0 \times 10^{-6}$ M
    • C.
      $2.0 \times 10^{-4}$ M
    • D.
      $4.0 \times 10^{-4}$ M
15. Question 151 mark · Acids and bases
    What is the pH of a 0.10 M solution of a weak monoprotic acid HA with $K_a = 1.0 \times 10^{-5}$?
    • A.
      1.0
    • B.
      2.5
    • C.
      3.0
    • D.
      5.0
16. Question 1610 marks · Acids and bases
    Weak-acid titration. A student titrates 25.0 mL of 0.100 M propanoic acid, $\mathrm{HC_3H_5O_2}$ ($K_a = 1.3 \times 10^{-5}$), with 0.100 M NaOH at $25^{\circ}\text{C}$, where $K_w = 1.0 \times 10^{-14}$. Two indicators are available: methyl red, which changes color between pH 4.4 and 6.2, and phenolphthalein, which changes color between pH 8.2 and 10.0.
    (a)

    Write the equation for the ionization of propanoic acid in water and calculate the pH of the acid solution before any NaOH is added.

    [2]
    (b)

    Calculate the volume of NaOH solution required to reach the equivalence point, and write the net ionic equation for the reaction that occurs during the titration.

    [2]
    (c)

    Calculate the pH of the solution after 12.5 mL of the NaOH solution has been added. Justify the method you use.

    [2]
    (d)

    Is the pH at the equivalence point less than, equal to, or greater than 7.0? Justify your answer with a chemical equation, and calculate the pH at the equivalence point.

    [2]
    (e)

    Which of the two indicators should the student use to detect the equivalence point? Explain your choice in terms of the shape of the titration curve.

    [2]
17. Question 174 marks · Electrochemistry
    Electrochemistry. A galvanic cell is constructed from a zinc electrode in 1.0 M $\mathrm{Zn(NO_3)_2}$ and a copper electrode in 1.0 M $\mathrm{Cu(NO_3)_2}$, connected by a salt bridge and an external wire. Standard reduction potentials: $\mathrm{Zn^{2+} + 2e^- \rightarrow Zn}$, $E^{\circ} = -0.76$ V; $\mathrm{Cu^{2+} + 2e^- \rightarrow Cu}$, $E^{\circ} = +0.34$ V. Faraday's constant $F = 96{,}500$ C per mole of electrons; molar mass of Cu $= 63.5$ g/mol.
    (a)

    Write the balanced overall cell reaction and calculate the standard cell potential.

    [1]
    (b)

    Identify the anode, and state the direction in which electrons flow through the external wire.

    [1]
    (c)

    In a separate electrolysis experiment, a current of 2.00 A is passed through aqueous $\mathrm{CuSO_4}$ for 1930 s. Calculate the mass of copper deposited at the cathode.

    [2]

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