Free energy and cell potential Knowledge-Based Practice

Questions

1. 1.

   In an operating electrochemical cell at 298 K, if the reaction quotient $Q$ is greater than 1, how do the non-standard cell potential ($E_{\text{cell}}$) and the non-standard Gibbs free energy change ($\Delta G$) compare to their standard-state values ($E^\circ_{\text{cell}}$ and $\Delta G^\circ$)?

   • A) $E_{\text{cell}} > E^\circ_{\text{cell}}$ and $\Delta G < \Delta G^\circ$
   • B) $E_{\text{cell}} < E^\circ_{\text{cell}}$ and $\Delta G > \Delta G^\circ$
   • C) $E_{\text{cell}} < E^\circ_{\text{cell}}$ and $\Delta G < \Delta G^\circ$
   • D) $E_{\text{cell}} > E^\circ_{\text{cell}}$ and $\Delta G > \Delta G^\circ$
2. 2.

   When an operating electrochemical cell reaches chemical equilibrium at constant temperature and pressure, which statement correctly identifies the values of its cell potential ($E_{\text{cell}}$) and reaction Gibbs free energy change ($\Delta G$)?

   • A) $E_{\text{cell}} = E^\circ_{\text{cell}}$ and $\Delta G = \Delta G^\circ$
   • B) $E_{\text{cell}} = 0$ and $\Delta G = \Delta G^\circ$
   • C) $E_{\text{cell}} = 0$ and $\Delta G = 0$
   • D) $E^\circ_{\text{cell}} = 0$ and $\Delta G^\circ = 0$
3. 3.

   For an electrochemical reaction occurring under standard-state conditions at 298 K, which combination of values for the standard cell potential ($E^\circ_{\text{cell}}$), standard Gibbs free energy change ($\Delta G^\circ$), and equilibrium constant ($K$) indicates a thermodynamically spontaneous forward process?

   • A) $E^\circ_{\text{cell}} < 0$, $\Delta G^\circ > 0$, and $K > 1$
   • B) $E^\circ_{\text{cell}} > 0$, $\Delta G^\circ > 0$, and $K < 1$
   • C) $E^\circ_{\text{cell}} > 0$, $\Delta G^\circ < 0$, and $K > 1$
   • D) $E^\circ_{\text{cell}} < 0$, $\Delta G^\circ < 0$, and $K < 1$
4. 4.

   When the stoichiometric coefficients of a balanced redox reaction are multiplied by a factor of 2, how are the standard cell potential ($E^\circ_{\text{cell}}$) and the standard Gibbs free energy change ($\Delta G^\circ$) affected?

   • A) $E^\circ_{\text{cell}}$ remains unchanged, whereas $\Delta G^\circ$ is multiplied by 2.
   • B) Both $E^\circ_{\text{cell}}$ and $\Delta G^\circ$ are multiplied by 2.
   • C) $E^\circ_{\text{cell}}$ is multiplied by 2, whereas $\Delta G^\circ$ remains unchanged.
   • D) $E^\circ_{\text{cell}}$ is squared, whereas $\Delta G^\circ$ is multiplied by 2.
5. 5.

   A galvanic cell operates via a two-electron transfer process with a standard cell potential of +0.50 V. Given that Faraday's constant is approximately 96,500 C/mol, what is the standard Gibbs free energy change ($\Delta G^\circ$) for this reaction?

   • A) +96.5 kJ/mol
   • B) -193 kJ/mol
   • C) -96.5 kJ/mol
   • D) +193 kJ/mol

Answers and step-by-step solutions appear after you finish the test.