5 Steps to a 5 AP Chemistry 2019

AP Chemistry Practice Exam 1 ❮ 315

25. If one of the containers sprang a small leak,
    which of the following would change?
    (A) Moles, temperature, and pressure
    (B) Moles and pressure
    (C) Temperature and pressure
    (D) Moles and temperature


26. The specific rate constant, k, for a certain first-
    order reaction is 86 h-^1. What mass of a 0.0500 g
    sample of starting material will remain after 58 s?
    (A) 0.0500 g
    (B) 0.0250 g
    (C) 0.0125 g
    (D) 0.00625 g

Use the information on the containers in the fol-

lowing diagram to answer questions 27-31 con-

cerning the following equilibrium:

CO(g) + 2 H 2 (g) ^ CH 3 OH(g)

CH 3 OH

Not equilibrium

C

CO

H 2

A

CO

H 2

B

CH 3 OH

CH 3 OH

Equilibrium

D

CO

H 2

27. Container A initially contains 0.60 mole of H 2
    and 0.60 mole of CO and is allowed to come to
    equilibrium. At equilibrium, there are 0.40 mole
    of CO in the flask. What is the value of Kc, the
    equilibrium constant, for the reaction?
    (A) 0.40
    (B) 2.5
    (C) 0.080
    (D) 12


28. A 1.00-mole sample of CH 3 OH is placed in con-
    tainer B and the system is allowed to go to equilib-
    rium. What can be said about the relative rates of
    reaction with respect to the various components?
    (A) The rate of CO formation is numerically
    equal to the rate of CH 3 OH loss.
    (B) The rate of H 2 formation is numerically
    equal to the rate of CH 3 OH loss.
    (C) The rate of H 2 (g) formation is half the rate of
    CO(g) formation.
    (D) The rate of H 2 (g) formation is equal to the
    rate of CO(g) formation.
    29. The mixture in container D is in equilibrium.
    Which of the following is true?
    (A) The rate of the forward and reverse reac-
    tions is equal to zero.
    (B) The rate of the forward reaction is equal to
    the rate of the reverse reaction.
    (C) The pressure in the system is increasing.
    (D) The pressure in the system is decreasing.
    30. The mixture in container A goes to equilibrium.
    If the initial moles of H 2 (g) is twice the initial
    moles of CO(g), which of the following is true?
    (A) Both reactants are limiting; therefore, the
    reaction will continue until there are zero
    moles of each remaining.
    (B) The total pressure of the system decreases
    until the system reaches equilibrium.
    (C) The total pressure of the system increases
    until the system equals equilibrium.
    (D) No reaction occurs until a catalyst is added.
    31. As the mixture in container B approaches equi-
    librium, the partial pressure of CH 3 OH gas
    decreases by 1.5 atm. What is the net change in
    the total pressure of the system?
    (A) +1.5 atm
    (B) +3.0 atm
    (C) -1.5 atm
    (D) -3.0 atm

Use the information on standard reduction poten-

tials in the following table to answer questions

32 - 36.

E ° (V)

F 2 (g) + 2 e- → 2 F-(aq) +2.87

Ag+(aq) + 1 e- → Ag(s) +0.80

O 2 (g) + 2 H 2 O(l) + 4 e- →

4 OH-(aq) +0.40

AgCl(s) + 1 e- → Ag(s) + Cl-(aq) +0.22

Pb^2 +(aq) + 2 e- → Pb(s) -0.13

NO 2 - (aq) + 5 H 2 O(l) + 6 e- →

NH 3 (aq) + 7 OH-(aq) -0.15

2 H 2 O(l) + 2 e- → H 2 (g) + 2 OH-(aq) -0.83

Cr^2 +(aq) + 2 e-→ Cr(s) -0.91

Al^3 +(aq) + 3 e- → Al(s) -1.66

Rb+(aq) + 1 e- → Rb(s) -2.93

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20-Moore_PE01_p307-340.indd 315 31/05/18 1:58 pm