The reagent used in the qualitative analysis | vedclass

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Question

(B) The $IV^{th}$ group basic radicals $(Co^{2+}, Ni^{2+}, Mn^{2+}, Zn^{2+})$ are precipitated as their sulphides in an alkaline medium. In the presen

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$H_2S$ (in alkaline medium)

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(B) The $IV^{th}$ group basic radicals $(Co^{2+}, Ni^{2+}, Mn^{2+}, Zn^{2+})$ are precipitated as their sulphides in an alkaline medium. In the presence of $NH_4OH$,the dissociation of $H_2S$ is increased due to the removal of $H^+$ ions by $OH^-$ ions,which shifts the equilibrium $H_2S \rightleftharpoons 2H^+ + S^{2-}$ to the right. This increases the concentration of $S^{2-}$ ions,allowing the solubility product of $IV^{th}$ group sulphides to be exceeded. Therefore,$H_2S$ in the presence of $NH_4OH$ (alkaline medium) is the correct reagent.

The reagent used in the qualitative analysis of the $IV^{th}$ group basic radicals is:

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