Question

The correct statement among the following is :

• A. For coagulation of aluminium hydroxide sol $B{a}^{2+}$ ions are more effective than $N{a}^{+}$
• B. Cellulose solution is an example of multimolecular colloid system
• C. Longer the length of hydrohobic chain, greater is the value of critical micelle concentration (CMC)
• D. Spontaneous adsorption of gases on solid surface is an exothermic process as entropy decreases during adsorption

Answer 1

The correct option is D Spontaneous adsorption of gases on solid surface is an exothermic process as entropy decreases during adsorption

(A) Aluminium hydroxide is positive sol. So, negative ions are effective in coagulation.

(B) Cellulose solution is an example of macromolecular colloid.

(C) CMC decrease with the increase in chain length of hydrophobic portion

(D) Spontaneous adsorption of gs implies $\Delta G$ is negative. The degree of randomness of gas molecules also decreases with adsorption. Hence $\Delta S$ is also negative.
Therefore, $T\Delta S$ is negative.
$\Delta H=\Delta G+T\Delta S$
Therefore, $\Delta H=-ve$
Hence, spontaneous adsorption of a gas on a solid surface is an exothermic process because $\Delta S$ decreases for the system.