Why does the concentration of copper sulphate remain constant during electrolysis of copper sulphate with a copper electrode?

State one relevant observation for of the following:

At the anode, when molten lead bromide is electrolyzed using graphite electrodes.

Name the gas that is produced in the following case:

At the anode during the electrolysis of acidified water.

State one observation for the following:

Copper sulphate solution is electrolysed using copper electrodes.

State one relevant reason for the following:

• Graphite anode is preferred to platinum in the electrolysis of molten lead bromide.