Question

Which equation describes the half-reaction that occurs at the cathode during the electrolysis of water? 4h+(aq + 4oh–(aq ? 4h2o(l 2h2o(l ? 2h2(g + o2(g o2(g + 4h+(aq + 4e– ? 2h2o(l 2h2o(l + 2e– ? h2(g + 2oh–(aq?

Answer 1

Answer: $2H_2O(l)+2e^-\rightarrow H_2(g)+2OH^-(aq)$

Explanation :

Electrolysis of water is defined as decomposition of water into oxygen gas and hydrogen gas due to the passage on an electric current. In electrolytic cell oxidation occurs at anode and reduction occurs at cathode. At anode we will get oxygen gas and at cathode we will get hydrogen gas.

Half reaction at anode:

$2H_2O(l)\rightarrow O_2(g)+H^+(aq)+4e^-$..(1)

Half reaction at cathode:

$2H_2O(l)+2e^-\rightarrow H_2(g)+2OH^-(aq)$..(2)

Overall reaction:(1)+(2)

$2H_2O(l)\rightarrow H_2(g)+O_2(g)$

Answer 2

Electrolysis of water involves the decomposition of water into oxygen and hydrogen gas by passing an electric current through water. The positively charged ion (hydrogen ion) moves to the negative electrode (cathode) during electrolysis, while the negatively charged ion (OH-) moves to the positive electrode (anode). Therefore, the half equation that occurs at the cathode during the electrolysis of water will be; 
4H+(aq) + 4e- = 2H2 (g)