Question

The action of heat of the blue crystalline solid L gives a reddish brown gas M, is which re-light a glowing splint and leave a black residue. When gas N, which has a rotten egg smell, is passed through a solution of L a black precipitate is formed.

1. Identify L, M and N (Name and formula).
2. Write the equation for the action of heat.
3. Write the equation for the reaction between the solution of L and the gas M.

Answer 1

i. L is copper nitrate [Cu(NO₃)₂]. 

M is nitrogen dioxide [NO₂].

N is hydrogen sulphide [H₂S].

ii. \[\ce{\underset{Blue crystalline}{2Cu(NO3)2} ->[heat] \underset{Black}{2CuO} + 4NO2 + O2}\]

iii. When a H₂S gas, which has a rotten egg smell, is passed through a solution of Cu(NO₃)₂, a black ppt. of CuS is formed.

\[\ce{Cu(NO3)2 + H2S ->CuS + 2HNO3}\]