Question 1

Which of the following statements is TRUE regarding the relationship between cell potential ($$E_\mathrm{cell}$$), Gibbs free energy ($$\Delta G$$), and the equilibrium constant ($$K$$)?

Accepted Answer

$$E_\mathrm{cell} \u003e 0$$, $$\Delta G  1$$

Question 2

Given the standard reduction potentials: $$\mathrm{Hg$$^{2+}$$ + 2e^- \rightarrow Hg(l)}$$, $$E^\circ = +0.85\ \mathrm{V}$$ and $$\mathrm{Cu$$^{2+}$$ + 2e^- \rightarrow Cu(s)}$$, $$E^\circ = +0.34\ \mathrm{V}$$, what is the standard cell potential for the reaction $$\mathrm{Hg$$^{2+}$$ + Cu(s) \rightarrow Hg(l) + Cu$$^{2+}$$}$$?

Accepted Answer

$$E^\circ_\mathrm{cell} = +0.51\ \mathrm{V}$$

Question 3

If a reaction has $$\Delta G^\circ = -237\ \mathrm{kJ}$$ and transfers 2 moles of electrons, what is the standard cell potential ($$E^\circ_\mathrm{cell}) at$$ $$25^\circ\mathrm{C}$$? Use $$F = 96,485\ \mathrm{C/mol\ e^-}.$$

Accepted Answer

$$E^\circ_\mathrm{cell} = +1.23\ \mathrm{V}$$

Question 4

Which equation correctly relates the standard cell potential to the equilibrium constant $$K at$$ $$25^\circ\mathrm{C}$$?

Accepted Answer

$$E^\circ_\mathrm{cell} = \dfrac{0.0592}{n} \log K$$

Question 5

A reaction has $$K = 1.5 	imes 10$$^{17}$$ at 30$$^\circ\mathrm{C}$$. What can you conclude about $$\Delta G^\circ$$ and E$$^\circ_\mathrm{cell}$$?

Accepted Answer

$$\Delta G^\circ  0$$

Question 6

For the reaction $$\mathrm{CH_4$(g) + CO_2$(g) \rightarrow 2CO(g) + 2H_2(g)} at$$ $$25^\circ\mathrm{C}$$, the equilibrium mixture contains $$0.255\ \mathrm{M}$$ $$\mathrm{CH_4$}$$, $$1.10\ \mathrm{M}$$ $$\mathrm{CO_2$}$$, $$0.380\ \mathrm{M}$$ $$\mathrm{CO}$$, and $$0.250\ \mathrm{M}$$ $$\mathrm{H_2$}. $$What is the expression for the reaction quotient $$Q$$?

Accepted Answer

$$Q = \dfrac{[CO]^2[H_2$]^2}{[CH_4$][CO_2$]}$$

Question 7

Given the reaction $$2\mathrm{Cl_2$(g)} + 2\mathrm{H_2O(l)} ightarrow 4\mathrm{HCl(g)} + \mathrm{O_2$(g)}$$, and $$K = 1.5 	imes 10$$^{17}$$ at 30$$^\circ\mathrm{C}$$, what is the sign of $$\Delta G^\circ$$ and what does this indicate about the spontaneity of the reaction?

Accepted Answer

$$\Delta G^\circ \u003c 0$$, reaction is spontaneous

Question 8

Which of the following correctly describes a spontaneous electrochemical reaction under standard conditions?

Accepted Answer

$$E^\circ_\mathrm{cell} \u003e 0$$, $$\Delta G^\circ  1$$

Question 9

If $$\Delta G^\circ$$ for a reaction is positive, what can you conclude about $$K$$ and $$E^\circ_\mathrm{cell}$$?

Accepted Answer

$$K \u003c 1$$ and $$E^\circ_\mathrm{cell} \u003c 0$$

Question 10

Which of the following is the correct formula for calculating the standard Gibbs free energy change from the standard cell potential?

Accepted Answer

$$\Delta G^\circ = -nFE^\circ_\mathrm{cell}$$

Question 11

A cell is constructed with the following half-reactions: $$\mathrm{Ag^+ + e^- \rightarrow Ag(s)}$$, $$E^\circ = +0.80\ \mathrm{V}$$ and $$\mathrm{Zn$$^{2+}$$ + 2e^- \rightarrow Zn(s)}$$, $$E^\circ = -0.76\ \mathrm{V}. $$What is the standard cell potential for the spontaneous reaction?

Accepted Answer

$$E^\circ_\mathrm{cell} = +1.56\ \mathrm{V}$$

Question 12

If the equilibrium constant $$K$$ for a reaction is much less than 1, what does this indicate about the cell potential and spontaneity?

Accepted Answer

$$E^\circ_\mathrm{cell} \u003c 0$$, reaction is nonspontaneous

Question 13

Which of the following is the correct Nernst equation for a cell at $$25^\circ\mathrm{C}$$?

Accepted Answer

$$E_\mathrm{cell} = E^\circ_\mathrm{cell} - \dfrac{0.0592}{n} \log Q$$

Question 14

A battery is considered 'dead' when $$E_\mathrm{cell}$$ reaches which value?

Accepted Answer

$$E_\mathrm{cell} = 0$$

Question 15

If a redox reaction involves the transfer of 4 electrons and has $$E^\circ_\mathrm{cell} = 0.30\ \mathrm{V}$$, what is the value of $$\Delta G^\circ$$? ($$F = 96,485\ \mathrm{C/mol\ e^-})$$

Accepted Answer

$$\Delta G^\circ = -115,782\ \mathrm{J}$$

Question 16

Which of the following best explains why a reaction with $$E^\circ_\mathrm{cell} \u003e 0 is $$spontaneous under standard conditions?

Accepted Answer

Because $$\Delta G^\circ is $$negative, indicating the reaction releases free energy

Cell Potential, Gibbs Free Energy, and Equilibrium Constant (Electrochemistry)

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