Cell potential, Gibbs energy and the equilibrium constant — NEET & JEE Questions

Question 1 · difficulty L1 · recall

For an electrochemical cell reaction transferring $n$ electrons, the standard Gibbs energy change is related to standard cell potential by

• A. $\Delta G^\circ=-nFE^\circ$
• B. $\Delta G^\circ=nFE^\circ$
• C. $\Delta G^\circ=-FE^\circ/n$
• D. $\Delta G^\circ=RT/E^\circ$

Question 2 · difficulty L2 · understanding

A spontaneous galvanic cell reaction under standard conditions has

• A. $E^\circ_{cell}>0$ and $\Delta G^\circ<0$
• B. $E^\circ_{cell}<0$ and $\Delta G^\circ<0$
• C. $E^\circ_{cell}=0$ always
• D. $E^\circ_{cell}>0$ and $\Delta G^\circ>0$

Question 3 · difficulty L2 · understanding

At equilibrium for the overall cell reaction, the cell potential is

• A. zero
• B. always 1 V
• C. infinite
• D. equal to $E^\circ$ for every system

Question 4 · difficulty L2 · understanding

The relation between standard Gibbs energy and equilibrium constant is

• A. $\Delta G^\circ=-RT\ln K$
• B. $\Delta G^\circ=RT\ln K$
• C. $\Delta G^\circ=-KRT$
• D. $K=-RT/\Delta G^\circ$

Question 5 · difficulty L3 · application

A cell has $E^\circ=1.10\,\text{V}$ and transfers 2 electrons. What is $\Delta G^\circ$ approximately? Take $F=96500\,\text{C mol}^{-1}$.

• A. $-212\,\text{kJ mol}^{-1}$
• B. $-106\,\text{kJ mol}^{-1}$
• C. $+212\,\text{kJ mol}^{-1}$
• D. $+106\,\text{kJ mol}^{-1}$

Question 6 · difficulty L3 · application

If $E^\circ_{cell}$ is negative for a reaction as written, what can be concluded under standard conditions?

• A. The reaction as written is non-spontaneous and the reverse is favoured
• B. The reaction is necessarily at equilibrium
• C. The reaction is spontaneous because voltage has a magnitude
• D. No thermodynamic conclusion can be drawn

Question 7 · difficulty L3 · application

At 298 K, a cell transfers 2 electrons and has $E^\circ=0.0591\,\text{V}$. Approximately what is $\log_{10}K$?

• A. 1
• B. 2
• C. 4
• D. 10

Question 8 · difficulty L3 · application

If $K=1$ for a cell reaction under standard-state definition at a given temperature, then

• A. $\Delta G^\circ=0$ and $E^\circ=0$
• B. $\Delta G^\circ<0$ and $E^\circ>0$
• C. $\Delta G^\circ>0$ and $E^\circ<0$
• D. $E^\circ$ must be 1 V

Question 9 · difficulty L4 · application

A cell reaction has $n=1$ and $E^\circ=0.1182\,\text{V}$ at 298 K. What is $K$ approximately?

• A. $10$
• B. $10^2$
• C. $10^4$
• D. $10^{-2}$

Question 10 · difficulty L4 · application

A reaction has $\Delta G^\circ=-57.9\,\text{kJ mol}^{-1}$ and transfers 2 electrons. Take $F=96500$. What is $E^\circ$ approximately?

• A. 0.15 V
• B. 0.30 V
• C. 0.60 V
• D. 1.20 V