Question

Assertion :$F{e}^{3+}$ can be used for coagulation of $A{s}_2{S}_3$ sol. Reason: $F{e}^{3+}$ reacts with $A{s}_2{S}_3$ to give $F{e}_2{S}_3$.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Metallic sulphides like $A{s}_2{S}_3$, $S{b}_2{S}_3$ and $CdS$ sols are example of negatively charged colloids. So, positive cation like $F{e}^{+3}$ can be used to coagulate these colloidal sols.
The reaction is as follows:
$F{e}^{+3}+A{s}_2{S}_3.S^{2-}\to A{s}_2{S}_3+F{e}_2{S}_3$
(negative colloid)