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.
Zinc
When sodium hydroxide is added to zinc sulphate, sodium sulphate is formed and zinc hydroxide is precipitated:
ZnSO4+2NaOH→Na2SO4+Zn(OH)2
The gelatinous white precipitate of Zn(OH)2 gets soluble if an excess of sodium hydroxide is added.
Zn(OH)2+2NaOH (excess)→Na2ZnO2 (aq)+H2O