Question

The concentration of electrolyte required to coagulate a given amount of $A{s}_2{S}_3$ sol is minimum in the case of :

• A. magnesium nitrate
• B. potassium nitrate
• C. potassium sulphate
• D. aluminium nitrate

Answer 1

The correct option is D aluminium nitrate

Arsenic sulphide $A{s}_2{S}_3$ is negatively charged sol. It will be coagulated by ions carrying positive charge. In aluminium nitrate, the charge on $Al$ cation is +3 which is maximum among given cations. Hence, aluminium nitrate has maximum coagulating power and minimum concentration of aluminium nitrate is required to coagulate arsenic sulphide sol.