Choose the correct answer from the options given : The inert electrode used in the electrolysis of acidified water is :

1. Nickle
2. Platinum
3. Copper
4. Silver

State one observation for the following : Copper sulphate solution is electrolysed using copper electrodes.

State one relevant reason for : Graphite anode is preferred to platinum in the electrolysis of molten lead bromide.

Arrange the following according to the instruction given in the bracket : Mg²⁺, Cu²⁺, Na¹⁺, H¹⁺ [In the order of preferential discharge at the cathode. ]