Identify the correct decreasing order of coagulating value of the following electrolytes when each of them is separately added to ${\mathrm{As}}_2{\mathrm{S}}_3$ sol(Assume all electrolytes are strong electrolytes).

detailed solution

Correct option is D

As2S3 is a negative sol. According to Hardy Schulze rule “A negative sol is most effectively coagulated by a cation with higher valency”.∴ coagulating power of Al+3>Ba+2>Na+ in the coagulation of As2S3 solution.Number of milli moles of electrolyte added to one litre of colloid to protect it from coagulation in two hours is called flocculating value or coagulating value.Coagulation power ∝1Coagulation value;Thus coagulating value of Al+3