Question

The Arsenous sulphide sol has negative charge. The maximum power of precipitating it is of

• A. $H_{2}S{O}_4$
• B. $N{a}_{3}P{O}_4$
• C. $CaC{l}_2$
• D. $AlC{l}_3$

Answer 1

The correct option is D $AlC{l}_3$

Hardy Schulze rule states that greater the valency of the oppositely charged ion of the electrolyte being added, the faster is the coagulation.
$A{s}_2{S}_3$ sol is a negatively charged sol and the charge on this can be neutralized by using a positively charged sol. Most precipitation will occur with $AlC{l}_3$ as Al has a 3+ charge. Order of precipitation with cations is: $A{l}^{3+}>C{a}^{2+}>N{a}^{+}>H^{+}$.