The hydroxide of which metal ion is soluble in excess of sodium hydroxide solution.
Al(OH)3 + NaOH → NaAlO2 + 2H2O
(Soluble)
Aluminium hydroxide dissolves in excess of Sodium hydroxide as sodium aluminate.
A metal salt (M) on reacting with sodium hydroxide forms sodium sulphate and a gelatinous white precipitate of a metal hydroxide. The precipitate is soluble in excess of sodium hydroxide. Identify M.