Q.

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

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a

Low S2- ion concentration is required to get precipitate

b

High S2- ion concentration is required to get precipitate

c

IIA group metal sulphides have higher values of Ksp than that of IVA group metal sulphides

d

pH value increases

answer is A.

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Detailed 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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