Consider the Daniell cell represented by . Which of the following experimental modifications will th — Electrochemistry Chemistry Question
Question
Consider the Daniell cell represented by $Zn(s) \| Zn^{2+}(aq, C_1) \|\| Cu^{2+}(aq, C_2) \| Cu(s)$. Which of the following experimental modifications will thermodynamically INCREASE the operating cell potential ($E_{cell}$)?
💡 Solution & Explanation
By the Nernst equation, $E_{cell} = E^\circ_{cell} - \frac{RT}{2F} \ln \frac{[Zn^{2+}]}{[Cu^{2+}]}$. To increase $E_{cell}$, the logarithmic term must decrease, requiring the ratio $\frac{[Zn^{2+}]}{[Cu^{2+}]}$ to decrease. This is achieved by either increasing the cathode concentration $[Cu^{2+}]$ ($C_2$) or decreasing the anode concentration $[Zn^{2+}]$ ($C_1$). Diluting the anode compartment with pure water effectively decreases $[Zn^{2+}]$, thus increasing $E_{cell}$. Adding solid $ZnS$ has negligible effect on the potential as the activity of a solid remains unity.