Give reasons for following observations:

(i) Leather gets hardened after tanning.

(ii) Lyophilic sol is more stable than lyophobic sol.

(iii) It is necessary to remove CO when ammonia is prepared by Haber’s process.

(i) Animal hide is made of positively charged colloidal particles while tannic acid or the other chemicals used for tanning are made up negatively charged colloidal particles. When these two come in contact during the process they coagulate thereby hardening the skin(hide).

(ii) Lyophilic sols not repel the dispersion medium i.e., they have high affinity to the solvent leading to high solvation which gives stability. Whereas lyophobic have no affinity to the solvent, so no stability due to solvation. They are stabilized only due to charge while lyophilic sol is stabilised due to both charge and solvation, hence more stable.

(iii) CO acts as poison on the iron catalyst used in this process, thereby lowering the efficiency of catalyst.