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Question: Which of the following has the highest coagulating power for sol \[A{{s}_{2}}\,{{S}_{3}}\]? A. \[S...

Which of the following has the highest coagulating power for sol As2 S3A{{s}_{2}}\,{{S}_{3}}?
A. SO42−SO_{4}^{2-}
B. Al3+A{{l}^{3+}}
C. PO43−PO_{4}^{3-}
D. K+{{K}^{+}}

Explanation

Solution

Hint: The coagulating power of Ions depends on the type of the SOL whether it is negative or positive. If the SOL is negative, the ion with highest positive charge will have the highest coagulating power and if the SOL is positive then the ion with highest negative charge will have highest coagulating power.

Complete answer:
Coagulation of a SOL is a phenomenon observed in surface chemistry. It is referring to the process by which the colloidal particles set. The colloidal particles undergoing the process of coagulation aggregate with each other. This aggregation forms larger particles. These large sized particles then settle down as precipitates.
Thus, the process of coagulation is also known as precipitation and flocculation. The process of precipitation is carried out or stimulated by the electrolytes which are added to the solution.
The smallest amount of an electrolyte which when added to the colloidal solution of 1 litre brings complete coagulation of the solution is known as the flocculation or coagulation value. The Colloidal Solutions are known as SOL. Sols are of two types- positive SOL and negative SOL.

Positive sols- They possess positive charge. All the sols of metal hydroxides are positive such as ferric hydroxide, aluminium hydroxide, etc. All basic dyes are also positive sols.
Negative sols-They possess negative charge. All the SOL of metal sulphides and those of acidic dyes are negative sols.
As2 S3A{{s}_{2}}\,{{S}_{3}} is a metal sulphide which justifies that it is a negatively charged SOL.
The ions which possess opposite charge with respect to that of particles of solution of colloid are most effective to bring the coagulation of the solution. These effective ions are referred to as coagulating ions or flocculating ions.
According to the above explanation the ion with positive charge will be most effective to cause coagulation of negative SOL. So, it will be most effective.

The correct answer is(B).

Note: If two ions with same charge are present then the effective one can be recognised by the following relation:
the more the ionic valency of the flocculating or coagulating ion the more is the ions capacity to bring about precipitation.