Question

Study the given figure and answer the question that follow :

(i) Why silica crucible is used in this type of electrolysis ?

(ii) Which anode is preferred and why ?

(iii) Why crucible is heated from outside ? 

(iv) Write the equations of the reaction which take place at the cathode and anode

Answer 1

(i) Silica is non-reactive. It can withstand at high temperature and is almost a non-conductor of electricity.

(ii) The graphite anode is preferred because it is unaffected by the reactive bromine vapours. 

(iii) The crucible is heated from outside to keep lead bromide in the molten sate. So that the ions become free.

(iv) At the cathode :

Pb²⁺ + 2e^- →   Pb

At the cathode :

Br^- -  e^-  → Br

Br  +  Br  → Br₂