Question

When the total cell emf of a voltaic cell is greater than zero, which of the following is true about the reaction quotient $Q$ and free energy change $\Delta\,G$ for the cell reaction?

• A. $Q$ is less than one and $\Delta\,G$ is greater than zero
• B. $Q$ is greater than one and $\Delta\,G$ is greater than zero
• C. $Q$ is less than one and $\Delta\,G$ is less than zero
• D. $Q$ is zero and $\Delta\,G$ is greater than zero
• E. $Q$ is greater than one and $\Delta\,G$ is less than zero

Answer 1

Answer: (E)

$ \Delta \,G=\Delta G^{\circ}+R T$ In $Q$

$\because \, \Delta G^{\circ}=-n F E^{\circ}$

and $E^{\circ}>\,0$

$\therefore \, \Delta G^{\circ}<\,0$

or $\Delta G-R T$ In $Q<\,0$

is possible when $Q>\,1$, and $\Delta G<\,0$