5 Steps to a 5 AP Chemistry 2019

316 ❯ STEP 5. Build Your Test-Taking Confidence

32. A student constructs an electrolysis cell with two
    inert electrodes in an aqueous solution that is
    1.0 M in rubidium nitrite, RbNO 2 , and 1.0 M in
    rubidium hydroxide, RbOH. As the cell operates,
    an odorless gas evolves from one electrode and a
    gas with a distinctive odor evolves from the other
    electrode. Choose the correct statement from the
    following list.
    (A) The odorless gas is oxygen.
    (B) The odorless gas is the result of reduction.
    (C) The gas with the distinctive odor is the
    result of oxidation.
    (D) The odorless gas evolves at the negative
    electrode.


33. There is a galvanic cell involving a lead, Pb,
    electrode in a 1.0 M lead(II) nitrate, Pb(NO 3 ) 2 ,
    solution and a chromium, Cr, electrode in a
    1.0 M chromium(II) sulfate, CrSO 4 , solution.
    What is the cell potential?
    (A) +0.78 V
    (B) -0.78 V
    (C) +1.04 V
    (D) 0.00 V


34. A student attempted to prepare an electrolysis
    cell to produce aluminum metal (Al) from an
    aqueous solution of aluminum chloride, AlCl 3 ,
    using a 6.0 V battery. The cathode compartment
    of the electrolysis contained 1.0 M aluminum
    chloride. The student was unsuccessful. Why was
    the student unable to produce aluminum metal?
    (A) The voltage from the battery was insuffi-
    cient to force the reaction to occur.
    (B) Reduction of chloride ion occurred in pref-
    erence to reduction of calcium ion.
    (C) Calcium chloride solutions do not conduct
    electricity.
    (D) Reduction of water occurred in preference
    to reduction of calcium ion.


35. Which of the substances in the table would be
    capable of reducing the aluminum ions in solid
    aluminum fluoride, AlF 3 , to aluminum metal?
    Assume the cell potentials in the table also apply
    to the solid state.
    (A) Cr(s)
    (B) Rb(s)
    (C) F 2 (g)
    (D) None
    36. A student constructs a galvanic cell that has a
    chromium, Cr, electrode in a compartment con-
    taining a 1.0 M chromium(II) nitrate, Cr(NO 3 ) 2 ,
    solution and a silver, Ag, electrode in a compart-
    ment containing 1.0 M silver nitrate, AgNO 3 ,
    solution. A salt bridge containing a 1.0 M
    potassium chloride, KCl, solution connects the
    two compartments. When the student mea-
    sures the cell potential, the value is far from the
    ideal predicted value. What is the cause of this
    discrepancy?
    (A) The initial concentrations should have been
    lower than 1.0 M.
    (B) The initial concentrations should have been
    higher than 1.0 M.
    (C) The potassium chloride in the salt bridge
    interfered with the reaction.
    (D) The student did not allow the cell to come
    to equilibrium.

Use the information on the acids in the following

diagram to answer questions 37-38.

Benzoic Acid

Ka 6.2 × 10–5

pKa 4.21

Chloroacetic Acid

14 × 10–3

2.86

Formic Acid

1.8 × 10–4

3.75

H

H C

Cl

H

C

O

O H

H C

O

O

H

H

C

C

C

C

H

H

C C

O

O

H

H

C

37. Sample solutions of each of the three acids were
    titrated with 0.10 M sodium hydroxide, NaOH.
    Each of the acid solutions had a concentration
    of 0.10 M. Which of the acid titrations had the
    highest pH at the endpoint?
    (A) Formic acid
    (B) Benzoic acid
    (C) Chloroacetic acid
    (D) They all had a pH of 7 at the endpoint.

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