Question

Using the above information, determine the standard reduction potential for the following reaction,
\[ 2M(s) + 3Zn^{2+}(aq) \rightarrow 2M^{3+}(aq) + 3Zn(s); \quad E^\circ = 0.90V \] \[ Zn^{2+}(aq) + 2e^- \rightarrow Zn(s); \quad E^\circ = -0.76V \]

• A. 0.90 V
• B. +1.66V
• C. -0.62 V
• D. -1.66 V

Hint:

Always apply $E^\circ_{\(\text{cell}} = E^\circ_{\(\text{cathode}} - E^\circ_{\(\text{anode}}$ to determine unknown electrode potentials.

Answer 1

The Correct Option is D

Let $E^\circ_{M^{3+}/M} = x$. Using the cell reaction and standard EMF: \[ E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}} = (-0.76) - x = 0.90 \Rightarrow x = -1.66\,V \]