Question

Question 49
What happens when?

(a) ${\text{ZnCO}}_3$ is heated in the absence of oxygen?
(b) a mixture of ${\text{Cu}}_2\text{O}$ and ${\text{Cu}}_2\text{S}$ is heated?

Answer 1

(a) It undergoes calcination (thermal decomposition). The reaction occurs as follows:

${\text{ZnCO}}_3\text{(s)}\stackrel{\text{Heat}}{\to }\text{ZnO(s)}+{\text{CO}}_2\text{(g)}$

(b) ${\text{Cu}}_2\text{O}$ undergoes auto reduction forming copper and sulphur dioxide. The reaction occurs as follows:

$2{\text{Cu}}_2\text{O(s)}+{\text{Cu}}_2\text{S(s)}\stackrel{\text{Heat}}{\to }6\text{Cu(s)}+{\text{SO}}_2\text{(g)}$