Question

why can we not use electrolytes in the solid form for electrolysis

Answer 1

because in solid form there will be no formation of ions

Answer 2

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Electrolysis

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Electrolysis of molten compounds

The ions in the electrolyte must be free to move to the electrodes for electrolysis to work. They are free to move in aqueous solutions and in molten liquids. However, the ions are in fixed positions in solid ionic compounds - they cannot move around, so electrolysis does not work in solids.



Ions in ionic solids are arranged in a giant lattice and cannot move around

When a molten (melted) ionic compound is electrolysed:

the positive ions are discharged at the cathode

the negative ions are discharged at the anode

For example, during the electrolysis of molten lead bromide:

lead ions, Pb2+, move to the cathode and are discharged as lead

bromide ions, Br–, move to the anode and are discharged as bromine

Half equations

You should be able to write half equations for the reactions happening at the electrodes during the electrolysis of a molten electrolyte if you are given the formulae of the ions it contains.

Example

Molten mead bromide contains Pb2+ ions and Br–ions. Write half equations for the electrode processes when it is electrolysed.

At the cathode: Pb2+ + 2e- → Pb

At the anode: 2Br- - 2e- → Br2