Question

Concentrated aqueous sodium hydroxide can separate a mixture of

• A. $Al^{3 +}$ and $Sn^{2 +}$
• B. $Al^{3 +}$ and $Fe^{3 +}$
• C. $Al^{3 +}$ and $Zn^{2 +}$
• D. $Zn^{2 +}$ and $Pb^{2 +}$

Answer 1

Answer: (B)

Concentrated aqueous sodium hydroxide can separate a mixture of $Al^{3 +}$ and $Fe^{3 +}$

$Al^{3 +}$ forms white gelatinous precipitate of $Al\left(O H\right)_{3}$ , which is soluble in excess of NaOH.

$Al\left(O H\right)_{3}+NaOH \rightarrow NaAlO_{2}+2H_{2}O$

$Fe^{3 +}$ forms reddish brown precipitate of $Fe\left(O H\right)_{3}$ , which is insoluble in excess of NaOH.