When H_2S is passed through a solution contai | vedclass

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(A) In qualitative analysis,$H_2S$ is a weak acid that dissociates as: $H_2S \rightleftharpoons 2H^+ + S^{2-}$.When $HCl$ is added,the concentration o

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The presence of $HCl$ decreases the concentration of sulfide ions.

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(A) In qualitative analysis,$H_2S$ is a weak acid that dissociates as: $H_2S \rightleftharpoons 2H^+ + S^{2-}$.When $HCl$ is added,the concentration of $H^+$ ions increases significantly due to the common ion effect.According to Le Chatelier's principle,this suppresses the dissociation of $H_2S$,thereby drastically reducing the concentration of $S^{2-}$ ions.Group $II$ cations precipitate at very low $S^{2-}$ concentrations,whereas group $IV$ cations require a higher concentration of $S^{2-}$ to exceed their solubility product $(K_{sp})$,which is not achieved in the presence of $HCl$.

When $H_2S$ is passed through a solution containing $HCl$ for qualitative analysis,it does not precipitate group $IV$ cations. Why is this?

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