Question

Among the electrolytes $\mathrm { Na } _ { 2 } \mathrm { SO } _ { 4 }$ , $\mathrm { CaCl } _ { 2 }$ and the most effective coagulating agent for the sol is

• A. (a) $\mathrm { Na } _ { 2 } \mathrm { SO } _ { 4 }$
• A. (b) $\mathrm { CaCl } _ { 2 }$
• A. (c) $\mathrm { Al } _ { 2 } \left( \mathrm { SO } _ { 4 } \right) _ { 3 }$
• A. (d) $\mathrm { NH } _ { 4 } \mathrm { Cl }$

Answer 1

(c)

Sol. $\mathrm { Sb } _ { 2 } \mathrm {~S} _ { 3 }$is a negatively charged sol. The most effective coagulating agent will be electrolyte with highest positive charge on the cation. Viz,

$\mathrm { Al } _ { 2 } \left( \mathrm { SO } _ { 4 } \right) _ { 3 }$ The order is

$\mathrm { Al } ^ { 3 + } > \mathrm { Ca } ^ { 2 + } > \mathrm { Na } ^ { + } > \mathrm { NH } _ { 4 } ^ { + }$