Question 1

Which element is oxidized in the reaction: $$\mathrm{Zn(s) + 2HCl(aq) \rightarrow $$ZnCl_2$$(aq) + H_2$(g)}$$?

Accepted Answer

Zinc

Question 2

What is the oxidation number of chromium in $$\mathrm{Cr_2O_7$$^{2-}$$}$$?

Accepted Answer

$$+6$$

Question 3

In a voltaic cell, which statement is correct?

Accepted Answer

Electrons flow from anode to cathode.

Question 4

Given the standard reduction potentials: $$\mathrm{Zn$$^{2+}$$ + 2e^- \rightarrow Zn(s)}$$ $$E^\circ = -0.76\ \mathrm{V}$$ and $$\mathrm{Ag^+ + e^- \rightarrow Ag(s)}$$ $$E^\circ = +0.80\ \mathrm{V}$$, what is the standard cell potential for the reaction $$\mathrm{Zn(s) + 2Ag^+(aq) \rightarrow Zn$$^{2+}$$(aq) + 2Ag(s)}$$?

Accepted Answer

$$1.56\ \mathrm{V}$$

Question 5

Which of the following best describes the function of a salt bridge in a voltaic cell?

Accepted Answer

It maintains electrical neutrality by allowing ion migration.

Question 6

A galvanic cell is constructed using a Fe electrode as the anode. Which metal can be used as the cathode to ensure a spontaneous reaction?

Accepted Answer

Copper

Question 7

Which equation correctly relates the standard cell potential $$E^\circ$$, Gibbs free energy $$\Delta G^\circ$$, and the equilibrium constant $$K$$?

Accepted Answer

$$E^\circ = \frac{RT}{nF} \ln K$$

Question 8

Which of the following statements about corrosion is correct?

Accepted Answer

Corrosion can be prevented by attaching a more easily oxidized metal as a sacrificial anode.

Question 9

What is the Nernst equation for a cell at $$25^\circC$$?

Accepted Answer

$$E = E^\circ - \frac{0.0592}{n} \log Q$$

Question 10

In the reaction $$\mathrm{Fe$$^{2+}$$ + H^+ + Cr_2O_7$$^{2-}$$ \rightarrow Fe$$^{3+}$$ + Cr$$^{3+}$$ + H_2O}$$, which element is reduced?

Accepted Answer

Chromium

Question 11

Which of the following is true for the standard hydrogen electrode (SHE)?

Accepted Answer

It is used as a reference with a potential defined as $$0.00\ \mathrm{V}.$$

Question 12

A battery is made by connecting two 1.5 V cells in series. What is the total voltage?

Accepted Answer

$$3.0\ \mathrm{V}$$

Question 13

Which of the following best describes electrolysis?

Accepted Answer

A nonspontaneous reaction driven by an external electric current.

Question 14

If $$\Delta G$$ for a redox reaction is negative, what can be said about the cell potential $$E_{cell}$$?

Accepted Answer

$$E_{cell} is $$positive.

Question 15

Which of the following metals will NOT protect iron from corrosion if used as a sacrificial anode?

Accepted Answer

Copper

Question 16

In the reaction $$\mathrm{$$MnO_4$$^- + C_2O_4$$^{2-}$$ \rightarrow Mn$$^{2+}$$ + CO_2$}$$, what is the change in oxidation state for manganese?

Accepted Answer

$$+7 to$$ $$+2$$

Question 17

Which of the following is a correct half-reaction for the reduction of $$\mathrm{Ag^+}$$?

Accepted Answer

$$\mathrm{Ag^+ + e^- \rightarrow Ag(s)}$$

Question 18

A voltaic cell is constructed with $$[\mathrm{Ni$$^{2+}$$}] = 2.80\ \mathrm{M}$$ and $$[\mathrm{Zn$$^{2+}$$}] = 0.130\ \mathrm{M}. If$$ $$E^\circ_{cell} = 0.50\ \mathrm{V}$$, what is the cell potential at $$25^\circC$$?

Accepted Answer

$$0.54\ \mathrm{V}$$

Electrochemistry: Principles, Applications, and Calculations

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