In contact process of manufacture of $\mathrm{H}_2 \mathrm{SO}_4$, the arsenic purifier used in the industrial plant contains

Observe the oxides $\mathrm{CO}, \mathrm{B}_2 \mathrm{O}_3, \mathrm{SiO}_2, \mathrm{CO}_2, \mathrm{Al}_2 \mathrm{O}_3$. $\mathrm{PbO}_2, \mathrm{Tl}_2 \mathrm{O}_3$. The number of acidic oxides in the list is

Which of the following when subjected to thermal decomposition will liberate dinitrogen ?

(i) Sodium nitrate

(ii) Ammonium dichromate

(iii) Barium azide

Identify the set which is not correctly matched in the following.