The hydroxide soluble in excess of sodium hydroxide solution but not in excess of ammonium hydroxide solution is:

1. Calcium hydroxide
2. Lead hydroxide
3. Magnesium hydroxide
4. Ferrous hydroxide

Lead hydroxide

Reason — Lead hydroxide, a white precipitate dissolves with excess of sodium hydroxide and gives colourless Sodium plumbite (Na₂[Pb(OH)₄]).

${\text{Pb(OH)}$2} + \underset{\text{excess}}{2\text{NaOH}} \longrightarrow \underset{\text{sodium plumbite - colourless}}{\text{Na}2\text{PbO}2↓} + 2\text{H}2\text{O}

Whereas, lead hydroxide is insoluble in excess of ammonium hydroxide (NH₄OH).

$\underset{\text{colourless}}{{\text{Pb(NO}$3)2}} + 2\text{NH}4\text{OH} \longrightarrow \underset{\text{white ppt}}{\text{Pb(OH)}2} ↓ + 2\text{NH}4\text{NO}3