Question

(a) What is selectivity of catalyst? Write example.
(b) What happens when hydrated ferric oxide sol is mixed with arsenius sulphide sol?
(c) Explain Tyndall effect with labelled diagram.

Answer 1

(a) Selectivity of catalyst:
The ability of catalyst to direct a reaction to yield a particular product.
For example, different products are obtained when different catalysts are used.
$CO+3H_2\stackrel{Ni}{\to }C{H}_4+H_{2}O$
$CO+2H_2\stackrel{Cu/ZnO-C{r}_2{O}_3}{\to }C{H}_{3}OH$
$CO+H_2\stackrel{Cu}{\to }HCO$
(b) When hydrated ferric oxide sol is mixed with arsenius sulphide sol, both sols are coagulated. Both sols have opposite charges. When they are mixed, their charges are neutralised. This results in mutual coagulation.

(c) Tyndall effect: It is scattering of light by colloidal particles and making the path of light visible through the dispersion.