Question

Concentrated aqueous sodium hydroxide can separate a mixture of

• A. $A{l}^{3+}$ and $S{n}^{2+}$
• B. $A{l}^{3+}$ and $F{e}^{3+}$
• C. $A{l}^{3+}$ and $Z{n}^{2+}$
• D. $Z{n}^{2+}$ and $P{b}^{2+}$

Answer 1

Answer: (B)

Concentrated aqueous sodium hydroxide can separate a mixture of $A{l}^{3+}$ and $F{e}^{3+}$

$A{l}^{3+}$ forms white gelatinous precipitate of $Al{\left(OH\right)}_3$ , which is soluble in excess of NaOH.

$Al{\left(OH\right)}_3+NaOH\to NaAl{O}_2+2H_{2}O$

$F{e}^{3+}$ forms reddish brown precipitate of $Fe{\left(OH\right)}_3$ , which is insoluble in excess of NaOH.