Question

Aluminium hydroxide is soluble in excess of sodium hydroxide forming the ion

• A. $ AlO_{3}^{-} $
• B. $ AlO_{2}^{3+} $
• C. $ AlO_{2}^{3-} $
• D. $ AlO_{2}^{-} $

Answer 1

Answer: (D)

Aluminium hydroxide is soluble in excess of sodium hydroxide forming the ion $AlO _{2}^{-}$.
$Al ( OH )_{3}+\underset{\text { excess }}{ NaOH } \longrightarrow \underset{
\text { sodium meta aluminate }}{ NaAlO _{2}}+2 H _{2} O$
$NaAlO _{2} \rightleftharpoons Na ^{+}+ AlO _{2}^{-}$
$ZnCl _{2}+2 NaOH \longrightarrow \underset{\text { white ppt. }}{ Zn ( OH )_{2}}$
$\xrightarrow{ NaOH } \underset{\text{ sodium zincate}}{Na _{2} ZnO _{2}}$
$Na _{2} ZnO _{2} \rightleftharpoons 2 Na ^{+}+ ZnO _{2}^{2-}$
$SnCl _{2}+2 NaOH \longrightarrow \underset{\text { white ppt. }}{ Sn ( OH )_{2}}$
$\xrightarrow{ NaOH }\underset{\text{sodium stannite}}{Na _{2} SnO _{2}}$