Which of the following radicals will not be p | vedclass

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(D) In qualitative inorganic analysis,the $II^{nd}$ group radicals (like $Cu^{2+}$,$Cd^{2+}$,$As^{3+}$,$Sb^{3+}$) are precipitated as sulphides by pas

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Cadmium

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(D) In qualitative inorganic analysis,the $II^{nd}$ group radicals (like $Cu^{2+}$,$Cd^{2+}$,$As^{3+}$,$Sb^{3+}$) are precipitated as sulphides by passing $H_2S$ gas in the presence of dilute $HCl$. However,the question asks which radical is not precipitated in a $concentrated$ acid solution. Actually,all these radicals ($Cu^{2+}$,$Cd^{2+}$,$As^{3+}$,$Sb^{3+}$) are precipitated as sulphides in the presence of $dilute$ $HCl$. If the acid concentration is too high,the common ion effect (due to $H^+$) suppresses the dissociation of $H_2S$,reducing the concentration of $S^{2-}$ ions. Among the given options,$CdS$ has the highest solubility product $(K_{sp})$ compared to $CuS$,$As_2S_3$,and $Sb_2S_3$. Therefore,$Cd^{2+}$ is the most likely to remain in solution if the acid concentration is increased significantly,preventing the precipitation of $CdS$.

Which of the following radicals will not be precipitated by passing $H_2S$ in a concentrated acid solution?

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