Question

The charge on $A{{s}_{2}}{{S}_{3}}$ sol is due to the adsorption of :
A. ${{H}^{+}}$
B. $O{{H}^{-}}$
C. ${{O}^{2-}}$
D. ${{S}^{2-}}$

Answer 1

Hint: The charge on the sol depends on the type of ion adsorbed. If negatively charged ions get adsorbed it gives negative sol whereas if positively charged ions get adsorbed it gives positive sol. The compound in the given question, $A{{s}_{2}}{{S}_{3}}$, produces arsenic cation and sulphide ion.

Complete Step by Step Solution:
A sol is defined as a colloidal suspension which is made out of tiny solid particles dispersed in a continuous liquid medium. Sols are actually stable and they show the Tyndall effect. Some examples of sols are blood, pigmented ink, cell fluids, paint, antacids and mud etc.

$A{{s}_{2}}{{S}_{3}}$ dissociates as tri positive arsenic cation and di negative sulphur anion. The above reaction can be given as follows-
$A{{s}_{2}}{{S}_{3}}\to A{{s}^{+3}}+{{S}^{2-}}$
Thus here $A{{s}_{2}}{{S}_{3}}$ can produce ${{S}^{2-}}$ ion or negatively charged sol. Thus the negative charge sol is formed due to the absorption of ${{S}^{2-}}$ or sulphur anion.

Again here $A{{s}_{2}}{{S}_{3}}$ can produce tri positive arsenic ion or positively charged sol but it is not formed actually all metal sulphides give negative sol.
Thus we can write that the charge on $A{{s}_{2}}{{S}_{3}}$ sol is due to the adsorption of ${{S}^{2-}}$ .
Thus the correct option is D.

Note: Here the nature of the sol form does not depend on the amount of $A{{s}_{2}}{{S}_{3}}$. If we use a large amount or small amount of $A{{s}_{2}}{{S}_{3}}$ it will always produce negatively charged sol.