Question

An electrochemical reaction is known to occur at +4.50 V against a Li$^+$/Li reference electrode. The potential of the same reaction against a Zn$^{2+}$/Zn reference electrode is _________. (Round off to two decimal places) Given standard electrode potentials: Li$^+$/Li : $E^\circ = -3.04$ V Zn$^{2+}$/Zn : $E^\circ = -0.76$ V

Hint:

To convert potentials between reference electrodes: 1. Convert the given value to absolute potential. 2. Subtract the standard potential of the new reference electrode.

Answer 1

Correct Answer: 2.2

The reaction potential relative to a new reference electrode is corrected by the difference in standard potentials. Given reaction potential vs Li/Li$^+$: \[ E_{\text{reaction vs Li}} = +4.50\ \text{V} \] Convert this to an absolute potential by adding Li reference potential: \[ E_{\text{abs}} = 4.50 + (-3.04) \] \[ E_{\text{abs}} = 1.46\ \text{V} \] Now convert absolute potential to Zn reference: \[ E_{\text{vs Zn}} = E_{\text{abs}} - E^\circ_{\text{Zn}} \] \[ E_{\text{vs Zn}} = 1.46 - (-0.76) \] \[ E_{\text{vs Zn}} = 2.22\ \text{V} \] Thus the potential of the reaction against the Zn$^{2+}$/Zn electrode is: \[ \boxed{2.22\ \text{V}} \]