10. A student 'tried to find out the standard reduction'potentials of copper electrode and Zinc eleetrode separately using Normal Hydrogen Electrode as reference electrode. He obtained the reduction potentials of `E^0 (Cu^(2))/ (Cu)` as `0.34` and `E^0 (zn^(2+)) / (zn)` as- `0.76 .` The, reference electrode acted here as cathode in one case and anode in theother.',
1. In which cases NHE acts as cathode and anode respectively.
2. Represent the electrode reactions of the NHE in both cases.
3. Represent the cell reaction when he used the Cu electrode and NHE.
4. Calculate the standard' potential of the cell constructed using `Zn` and Cu electrodes.

Explanation

I. With Zinc-electrode NHE acts as cathode and with copper electrode it acts as-anode:
2. As cathode `: H^*+l e 1 / 2 H_2`
As anode : `1 / 2 H_2 H^*+le^-`
3. `Cu^2++H, Cu+2 H^+`
4. `E_ on ^*=E_ cathode ^0-E_ anode ^0 - ` `=0.34=0.76=1.1` Volt