Question

The concentration of electrolyte required to coagulate a given amount of $As_2S_3$ sol. is minimum in the case of :

• A. Potassium sulphate
• B. Aluminium nitrate
• C. Magnesium nitrate
• D. Potassium nitrate

Answer 1

Answer: (B)

Aluminium nitrate

Answer 2

Arsenic sulphide $As_2S_3$ 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.