Q: For the reaction $$\mathrm{4Ag(s) + O_2$(g) + 4H^+(aq) \rightarrow 4Ag^+(aq) + 2H_2O(l)}$$, if $$E^\circ_{cell} = 0.43\ \mathrm{V}$$, what is the standard free energy change ($$\Delta G^\circ) at 298 K$$? ($$F = 96,485\ \mathrm{C/mol})$$

$$\Delta G^\circ = -nFE^\circ_{cell} = -4 \times 96,485 \times 0.43 = -1.7 \times 10^5$\ \mathrm{J}$$

Question 1

Which of the following statements best describes what occurs at the anode in a galvanic cell?

Accepted Answer

Oxidation occurs and electrons are released into the external circuit.

Question 2

Given the following redox reaction: $$\mathrm{Zn(s) + Cu$$^{2+}$$(aq) \rightarrow Zn$$^{2+}$$(aq) + Cu(s)}$$, which species is the oxidizing agent?

Accepted Answer

$$\mathrm{Cu$$^{2+}$$(aq)}$$

Question 3

What is the standard cell potential ($$E^\circ_{cell}) $$for the reaction $$\mathrm{Zn(s) + Cu$$^{2+}$$(aq) \rightarrow Zn$$^{2+}$$(aq) + Cu(s)}$$ given $$E^\circ_{red}(Cu$$^{2+}$$/Cu) = 0.34\ \mathrm{V}$$ and $$E^\circ_{red}(Zn$$^{2+}$$/Zn) = -0.76\ \mathrm{V}$$?

Accepted Answer

$$1.10\ \mathrm{V}$$

Question 4

Which of the following is the correct balanced half-reaction for the reduction of permanganate ion ($$\mathrm{$$MnO_4$$^-}) to$$ $$\mathrm{Mn$$^{2+}$$} in $$acidic solution?

Accepted Answer

$$\mathrm{$$MnO_4$$^-}(aq) + 8H^+(aq) + 5e^- \rightarrow Mn$$^{2+}$$(aq) + 4H_2O(l)}$$

Question 5

A voltaic cell is constructed with the following cell notation: $$\mathrm{Zn(s) | Zn$$^{2+}$$(aq) || Cu$$^{2+}$$(aq) | Cu(s)}. $$Which direction do electrons flow in the external circuit?

Accepted Answer

From Zn electrode to Cu electrode

Question 6

Which of the following correctly describes the function of the salt bridge in a galvanic cell?

Accepted Answer

It allows the migration of ions to maintain electrical neutrality.

Question 7

Using the Nernst equation, which of the following will decrease the cell potential ($$E_{cell}) $$for a galvanic cell?

Accepted Answer

Increasing the concentration of products relative to reactants

Question 8

For the reaction $$\mathrm{4Ag(s) + O_2$(g) + 4H^+(aq) \rightarrow 4Ag^+(aq) + 2H_2O(l)}$$, if $$E^\circ_{cell} = 0.43\ \mathrm{V}$$, what is the standard free energy change ($$\Delta G^\circ) at 298 K$$? ($$F = 96,485\ \mathrm{C/mol})$$

Accepted Answer

$$\Delta G^\circ = -nFE^\circ_{cell} = -4 	imes 96,485 	imes 0.43 = -1.7 	imes 10^5$\ \mathrm{J}$$

Question 9

Which of the following is the correct relationship between the equilibrium constant $$K$$ and the standard cell potential $$E^\circ_{cell}$$?

Accepted Answer

$$E^\circ_{cell} = \dfrac{RT}{nF} \ln K$$

Question 10

A student sets up a voltaic cell at 25°C with $$[Zn$$^{2+}$$] = 0.10\ \mathrm{M}$$ and $$[Cu$$^{2+}$$] = 1.0\ \mathrm{M}. $$Using the Nernst equation, what is the cell potential? ($$E^\circ_{cell} = 1.10\ \mathrm{V}$$, $$n = 2)$$

Accepted Answer

$$E_{cell} = 1.10 - \dfrac{0.0257}{2} \ln \dfrac{0.10}{1.0} = 1.10 - (0.01285)(-2.30) = 1.13\ \mathrm{V}$$

Question 11

Which of the following best explains why the blue color of the $$Cu^{2+}$$ solution fades as the reaction $$Zn(s) + Cu$$^{2+}$$(aq) \rightarrow Zn$$^{2+}$$(aq) + Cu(s)$$ proceeds?

Accepted Answer

$$Cu^{2+}$$ ions are reduced to $$Cu(s)$$, decreasing their concentration in solution.

Question 12

In the reaction $$MnO_4^-(aq) + C_2O$$_$$4^{2-}(aq) + H^+(aq$$) \rightarrow $$Mn^{2+}(aq$$) + $$CO_2(g) + H_2O(l$$)$$, what is the total number of electrons transferred when the equation is balanced?

Accepted Answer

10 electrons

Question 13

Which of the following is the correct cell notation for a galvanic cell based on the reaction $$2Al(s) + 3Cu$$^{2+}$$(aq) \rightarrow 2Al$$^{3+}$$(aq) + 3Cu(s)$$?

Accepted Answer

$$Al(s)|Al$$^{3+}$$(aq)||Cu$$^{2+}$$(aq)|Cu(s)$$

Question 14

If the equilibrium constant $$K$$ for a redox reaction is much greater than 1, what can be inferred about the standard cell potential $$E^\circ_{cell}$$?

Accepted Answer

$$E^\circ_{cell} is $$positive

Question 15

Which of the following best describes the role of $$NO_3$$^-$$ ions in the salt bridge of a voltaic cell?

Accepted Answer

They migrate toward the anode to balance the increase in positive charge.

Question 16

Which of the following is the correct expression for the Nernst equation?

Accepted Answer

$$E_{cell} = E^\circ_{cell} - \dfrac{RT}{nF} \ln Q$$

Electrochemistry: Redox Reactions, Galvanic Cells, and Cell Potentials

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