Question 1

Which of the following statements correctly describes the role of the salt bridge in a voltaic cell?

Accepted Answer

It maintains electrical neutrality in the half-cells via migration of ions.

Question 2

In the following cell notation: Pt | $$Fe^{2+}(aq$$), $$Fe^{3+}(aq$$) || $$Ni^{2+}(aq$$) | Ni(s), what is the reducing agent?

Accepted Answer

$$Fe^{2+}(aq)$$

Question 3

Which transformation could take place at the anode of an electrochemical cell?

Accepted Answer

NO \rightarrow $$NO_3^-$$

Question 4

Given the following reaction: Zn(s) + $$Cu^{2+}(aq$$) ightarrow $$Zn^{2+}(aq) + Cu(s$$), E^\circ = +1.10	ext{ V}. Which metal is oxidized?

Accepted Answer

Zinc

Question 5

Calculate the standard cell potential for the following reaction: Mg(s) + $$Cu^{2+}(aq$$) ightarrow Cu(s) + $$Mg^{2+}(aq). $$Given: $$Cu^{2+}(aq) + 2e$$^- ightarrow Cu(s), E^\circ = 0.34	ext{ V}; $$Mg^{2+}(aq) + 2e$$^- ightarrow Mg(s), E^\circ = -2.37	ext{ V}.

Accepted Answer

$$E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode} = 0.34 - (-2.37) = 2.71	ext{ V}$$

Question 6

Which metal will dissolve in $$HNO_3$$ but not in HCl, based on the activity series?

Accepted Answer

Au

Question 7

What is the relationship between the standard cell potential ($$E^\circ_{cell}$$), Gibbs free energy ($$\Delta G^\circ$$), and the equilibrium constant ($$K$$)?

Accepted Answer

$$\Delta G^\circ = -nFE^\circ_{cell}$$, $$\Delta G^\circ = -RT \ln K$$, $$E^\circ_{cell} = \frac{0.0592	ext{ V}}{n} \log K$$

Question 8

A concentration cell is assembled with a copper anode and cathode. One cell has [$$Cu^{2+}$$] = 0.25	ext{ M} and the other has [$$Cu^{2+}$$] = 2.5	ext{ M}. What is the cell potential?

Accepted Answer

$$E_{cell} = 0.030	ext{ V}$$

Question 9

Which of the following is true for a spontaneous electrochemical reaction under standard conditions?

Accepted Answer

$$\Delta G^\circ  0$$, $$K \u003e 1$$

Question 10

What is the cell potential for a voltaic cell having one electrode composed of a Zn strip dipped in a 0.025 M Zn($$NO_3)_2(aq) $$solution and the other electrode composed of a Zn strip dipped into a 0.500 M Zn($$NO_3)_2(aq) $$solution? Assume all other cell components are in place and the temperature is 25.0°C.

Accepted Answer

$$E_{cell} = 0.0592 \log \left( \frac{0.500}{0.025} \right)$$

Question 11

In a lead-acid storage battery, which reaction occurs at the anode during discharge?

Accepted Answer

$$Pb(s) + $$HSO_4$$^-(aq) \rightarrow $$PbSO_4$$(s) + H^+(aq) + 2e^-$$

Question 12

Which statement best describes the standard hydrogen electrode (SHE)?

Accepted Answer

It is used as the reference electrode with a defined potential of $$E^\circ = 0	ext{ V}.$$

Question 13

If the cell potential ($$E^\circ_{cell}) $$for a reaction is negative, what does this indicate about the reaction?

Accepted Answer

The reaction is nonspontaneous under standard conditions.

Question 14

Which of the following statements about electrolysis is correct?

Accepted Answer

Electrolysis uses electrical energy to drive a nonspontaneous chemical reaction.

Question 15

How many grams of aluminum can be plated out of a molten aluminum salt over the course of 30 minutes if 15 amps of electricity are employed? $$(Al^{3+} + 3e$$^- \rightarrow Al, 1 mol Al = 26.98 g, F = 96485 C/mol e^-)

Accepted Answer

8.43 g

Question 16

Which of the following methods is commonly used to prevent corrosion of iron?

Accepted Answer

Attaching iron to a more reactive metal such as magnesium (sacrificial electrode).

Question 17

In a hydrogen-oxygen fuel cell, which reaction occurs at the cathode?

Accepted Answer

$$O_2(g) + 2H_2O(l) + 4e$$^- \rightarrow 4OH^-(aq)$$

Electrochemistry: Redox Reactions, Electrochemical Cells, and Applications

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