In the precipitation of the group III in qual | vedclass

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(A) In qualitative analysis,group $III$ cations (like $Fe^{3+}$,$Al^{3+}$,$Cr^{3+}$) are precipitated as their hydroxides using $NH_4OH$ in the presen

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decrease concentration of $OH^{\ominus}$ ions

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(A) In qualitative analysis,group $III$ cations (like $Fe^{3+}$,$Al^{3+}$,$Cr^{3+}$) are precipitated as their hydroxides using $NH_4OH$ in the presence of $NH_4Cl$. $NH_4Cl$ is a strong electrolyte that dissociates completely to provide a high concentration of $NH_4^{+}$ ions. According to the common ion effect,the presence of excess $NH_4^{+}$ ions suppresses the dissociation of the weak base $NH_4OH$ $(NH_4OH \rightleftharpoons NH_4^{+} + OH^{\ominus})$. This significantly decreases the concentration of $OH^{\ominus}$ ions,ensuring that only the hydroxides of group $III$ cations precipitate,while preventing the precipitation of group $IV$ cations.

In the precipitation of the group $III$ in qualitative analysis,ammonium chloride is added before adding ammonium hydroxide to:

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