Question

A current is passed through an aqueous solution which on will decompose

Answer 1

The aqueous solution contains lithium ions Li+ and Bromide ions, Li- .

Oxidation is increase in oxidation number, which is caused by loss of electrons. Oxidation occurs at the electrode called the anode.

Reduction is decrease gain in oxidation number which is caused by gain of electrons. Reduction occurs at the cathode.

These are definitions used by CHEMISTS. There are other definitions.

At the anode, Bromide ions are stripped of their extra electrons and oxidized to bromine atoms which join together to make Br2, elemental bromine.

At the cathode, Lithium ions (Which in this case is negative) are supplied with electrons to replace the ones they lost when they became ions. They become neutral lithium atoms. Lithium atoms are more active than hydrogen so they react with water replacing hydrogen in water molecules. The displaced hydrogen atoms join in pairs to make H2, molecular hydrogen. The water molecules that have lost H become OH- ions,

So: 2Li+ + 2Br- ——-> H2 + Br2 + 2OH-

As half reactions:

At the Cathode: 2Li+ + 2e- ——-> 2 Li followed by 2 Li + H2O —-> Li+ +OH- + H2

and at the anode: 2 Br- ——-> Br2 + 2 e-