Question

Under standard-state conditions, which of the following half-reactions occurs at the cathode during the electrolysis of aqueous nickel sulfate at 25°C?

a. 2H2O ? O2 + 4H+ + 4e–
b. Ni2+ + 2e– ? Ni
c. 2H2O + 2e– ? H2 + 2OH–
d. Ni ? Ni2+ + 2e–

Answer 1

The following reaction will occur at cathode:

`Ni^(+2)(aq)+2e--->Ni(s)`

Step-by-step explanation:

The two half reaction during electrolysis of aqueous nickel sulfate will be

a) anode reaction :

Water will undergo oxidation and will evolve oxygen gas at anode as shown in the given reaction:

`2H_(2)O(l) ----> O_(2)(g) + 4H^(+)(aq) + 4e`

b) Cathode reaction: The reduction of Nickel ion will occur by gain of two electrons as shown in the given equation:

`Ni^(+2)(aq)+2e--->Ni(s)`

Thus the overall reaction will be:

`2H_(2)O(l) + 2Ni^(+2)----> O_(2)(g) + 4H^(+)(aq) + 2Ni(s)`