Question

A reddish brown metal x on heating forms a black coating on its surface. Metal does not react with hcl or h2so4.

Answer 1

the reddish brown metal is copper cu

on heating it reacts with atmospheric oxygen to form CuO

                                         2Cu + O2 --------  2CuO

this metal does not react with any mineral acids like hcl or h2so4 because copper is less reactive than hydrogen therefore it cant displace it.

Answer 2

Cu. +O2. cuo

Reddish. Heat Black

Brown