Which element on treatment with caustic soda solution produces `H_(2)` gas?

When zinc metal is heated with caustic soda solution, the gas evolved is

Caustic soda solution is an absorbent for:

The drain cleaner, Drainex, contains aluminium which reacts with caustic soda to produce H_2 . What volume of H_2 at 20^@C and 1 bar will be increased when 0.15 g of Al reacts?

Carborundum on heating with caustic soda in presence of air produces