AP Chemistry · Topic 7.6

Properties of the Equilibrium Constant Practice

Part of Equilibrium.(TRA-7.D)

Practice questions

6

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Sample questions

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  1. Sample 1difficulty 2/5

    If K_fwd = 4, K_rev =

    • A

      0.25

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    • B

      4

    • C

      16

    • D

      −4

    Why

    K for reverse = 1/K_fwd = 1/4 = 0.25.

  2. Sample 2difficulty 3/5

    K_p and K_c are related by

    • A

      K_p = K_c/T

    • B

      K_p = K_c(RT)^Δn

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    • C

      K_p = K_c·R·T

    • D

      K_p = K_c·n

    Why

    Δn = (moles gas products) − (moles gas reactants).

  3. Sample 3difficulty 4/5

    A ⇌ B has K=2; B ⇌ C has K=3. K for A ⇌ C is

    • A

      1

    • B

      6

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    • C

      5

    • D

      0.67

    Why

    Add reactions → multiply K's: 2 × 3 = 6.

  4. Sample 4difficulty 4/5

    At 500 K, KpK_p = 1.5 for N2O4(g)2NO2(g)N_2O_4(g) \rightleftharpoons 2NO_2(g). What is KcK_c? (R = 0.08206 L·atm/mol·K)

    • A

      Kc=0.244K_c = 0.244

    • B

      Kc=0.0366K_c = 0.0366

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    • C

      Kc=1.50K_c = 1.50

    • D

      Kc=61.5K_c = 61.5

    Why

    Kp=Kc(RT)ΔnK_p = K_c(RT)^{\Delta n} with Δn\Delta n = 2-1 = 1. KcK_c = Kp/(RT)K_p/(RT) = 1.5/((0.08206)(500)) = 1.5/41.03 = 0.0366.

  5. Sample 5difficulty 4/5

    For 2 NO2_2(g) ⇌ N2_2O4_4(g), Δn(gas) = 1 − 2 = −1. The relation between Kp and Kc is

    • A

      Kp = Kc

    • B

      Kp = Kc2^2

    • C

      Kp = Kc(RT)Δn^{Δn} = Kc/(RT)

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    • D

      Kp = Kc × RT

    Why

    Kp=Kc(RT)ΔnK_p = K_c (RT)^{\Delta n} where Δn = mol gas products − mol gas reactants. Here Δn = −1, so Kp=Kc/(RT)K_p = K_c/(RT).

AP Chemistry · 7.6 Properties of the Equilibrium Constant — Practice Questions | Acemy