Question

Question 39

On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed

(a) Write a balanced chemical equation of the reaction.
(b) Identity the brown gas X evolved.
(c) Identity the type of reaction.
(d) What could be the pH range of aqueous solution of the gas X?

Answer 1

(a) Balanced chemical equation:

$2{\text{Cu(NO}}_3{)}_2\text{(s)}\stackrel{\text{Heat}}{\to }2\text{CuO (s)}+{\text{O}}_2\text{(g)}+4{\text{NO}}_2\text{(g)}$

(b) The brown gas X evolved is nitrogen dioxide, $\left({\text{NO}}_2\right)$.

(c) This is a decomposition reaction as single reactant is decomposing to form three products.

(d) Nitrogen dioxide dissolves in water to form an acidic solution. Therefore, pH of this solution is less than 7. The reaction occurs as follows:

$2{\text{NO}}_2\text{(g)}+{\text{H}}_2\text{O (l)}\to {\text{HNO}}_2\text{(aq)}+{\text{HNO}}_3\text{(aq)}$