Question

A metal x does not liberate hydrogen gas hen it reacts with hcl but reacts with oxygen to form a black coloured compound y. When hydrogen as is passed over this heated compound again we get metal x. What is x and y

Answer 1

Metal X is copper because copper can't liberate H2 even with conc. HCl

2Cu + O2 = 2CuO
CuO is the black coloured compound.

CuO + H2 = Cu + H2O.

Hence,
Metal X= Cu
Compound Y = CuO