Question

A reddish brown vessel developed a green colored solid 'x' when left to open air for long time. When reacted with dil H2SO4, it forms a blue color solution along brisk effervesance due to colorless and odourless gas 'z'. 'x' decomposes to form black colored oxide of 'y' of a reddish brown metal along with gas 'z'. Identify x, y, and z ?

Answer 1

The solid (X) is copper carbonate. When it reacts with H2SO4 it forms CuSO4, which is blue and the colorless and odorless CO2 (Z).
Also copper carbonate decomposes to copper oxide (Y) and CO2 (Z).

Answer 2

X is Copper Carbonate $(CuCO_3)$

Y is Copper Oxide $(CuO)$

Z is Carbon dioxide $(CO_2)$

Explanation:

When left in the open air for some time, a vessel of copper which is reddish brown in color combines with carbon dioxide and also the moisture in the environment to form a green coating. This green coating is copper carbonate $(CuCO_3)$ which is basic in nature.

On reacting with dilute $H_2SO_4$, copper carbonate forms a blue colored solution. This solution is that of copper sulphate $(CuSO_4)$ and a colorless and odorless gas which is carbon dioxide $(CO_2)$.

On decomposition, copper carbonate forms copper oxide (CuO) which is black in color. It also decomposes to form carbon dioxide.