H_2S gas,when passed through a solution conta | vedclass

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(A) $H_2S$ is a weak electrolyte and undergoes dissociation as: $H_2S \rightleftharpoons 2H^+ + S^{2-}$.According to the common ion effect,the presenc

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Presence of $HCl$ decreases the sulphide ion concentration

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(A) $H_2S$ is a weak electrolyte and undergoes dissociation as: $H_2S \rightleftharpoons 2H^+ + S^{2-}$.According to the common ion effect,the presence of $HCl$ (a strong electrolyte) provides a high concentration of $H^+$ ions.This suppresses the ionization of $H_2S$,thereby significantly decreasing the concentration of $S^{2-}$ ions.The solubility product $(K_{sp})$ of group $II$ sulphides is very low,so even a low concentration of $S^{2-}$ is sufficient to exceed the ionic product and cause precipitation.However,the $K_{sp}$ of group $IV$ sulphides is relatively higher,and the suppressed $S^{2-}$ concentration is insufficient to cause their precipitation.

$H_2S$ gas,when passed through a solution containing $HCl$,precipitates the cations of group $II$ of qualitative analysis but not those belonging to the fourth group. This is because:

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