First slide

Solubility product(KSP)

Question

In qualitative analysis, to identify the II_A group sulphides, HCl is added to salt solution before the addition of H₂S. Because

Easy

A

Low S^2- ion concentration is required to get precipitate
B

High S^2- ion concentration is required to get precipitate
C

II_A group metal sulphides have higher values of K_sp than that of IV_A group metal sulphides
D

pH value increases

Solution

HCl is added before adding H₂S, So that the dissociation of H₂S is suppressed in presence of HCl due to common ion effect. This is desired as the solubilities of group II Cations is less and a low concentration of S^-2 ions is sufficient to precipitate their sulphides.
If HCl is not added, then S^-2 ion concentration will be high enough to precipitate group IV cations.

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