AP Chemistry Practice Exam #6

An oxidizing agent will cause which of the following changes?

• PtO₂ → PtO

• PtO₃ → PtO₂

• Pt(OH)₂ → Pt

• Pt(OH)₂²⁺ → PtO₃

• Pt(OH)₃²⁺ → PtO

Which of the following reactions is a redox reaction?

• K₂CrO₄ + BaCl₂ → BaCrO₄ + 2KCl

• Pb²⁺ + 2Br- → PbBr₂

• Cu + S → CuS

• all of these

Which of the following transformations could take place at the cathode of an electrochemical cell?

• MnO2 → MnO4-

• Br2 → BrO3-

• NO → HNO2

• HSO4- → H2SO3

• Mn2+ → MnO4-

The respective standard reduction potentials in V for Ni2+ and Ag+ are -0.28 and +0.80. The oxidizing agent in a cell based on nickel and silver is

• Ni

• Ni2+

• Ag+

• Ag

• the salt bridge

Referring to the image above, what changes occur when the cell is in operation? (Hint: Cu is a noble metal and is below hydrogen on the activity series. Write a reaction.)

• Anode: [H₃O⁺] increases Cathode: electrode increases in mass

• Anode: [H₃O⁺] increases Cathode: electrode decreases in mass

• Anode: [H₃O⁺] decreases Cathode: electrode increases in mass

• Anode: [H₃O⁺] decreases Cathode: electrode decreases in mass

• Anode: [H₃O⁺] remains constant Cathode: electrode increases in mass

In which of the following situations will a reaction be observed after 10 minutes? (Hint: create your own activity series from the reduction potentials.)

• A silver strip is placed in 1 M Pb(NO3)2.

• A lead strip is placed in 1 M Mg(NO3)2

• A zinc strip is placed in 1 M Mg(NO3)2

• A magnesium strip is placed in 1 M Zn(NO3)2

• A lead strip is placed in a 1 M Zn(NO3)2

Respective standard reduction potentials (in V) for Pb2+ and Ni2+ are -0.13 and -0.28. Which substance will be oxidized in the voltaic cell?

• Pb²⁺

• Pb

• Ni²⁺

• Ni

Given the following information, which of the statements is true:

• H⁺ is incapable of being oxidized or reduced

• Sn²⁺ is the weakest oxidizing agent

• Ni_(s) is the strongest oxidizing agent

• Li_(s) is the strongest reducing agent

• Li⁺_(aq) is the strongest reducing agent

Find the standard reduction potential for the reaction: In⁺³ + 3e- → In

• 0.34 V

• –0.34 V

• 1.02 V

• –1.02 V

• 0.00 V

A voltaic cell consists of a combination of a standard silver electrode and standard hydrogen electrode as shown in the image above. E° = Ag⁺/Ag = 0.80 V. Which of the following is FALSE?

• The overall cell potential depends on the difference in concentration between the two solutions.

• Hydrogen ion is being reduced.

• The overall cell potential is positive so the cell works.

• Hydrogen gas is being oxidized.

• The pH in the standard hydrogen electrode decreases.