The correct option is(A): 1 and 2.
Only \(\left( NH _{4}\right)_{2} Cr _{2} O _{7}\) and \(NH _{4} NO _{2}\) give \(N _{2}\) on
heating.
(i) \(\left( NH _{4}\right)_{2} Cr _{2} O _{7} \stackrel{\Delta}{\longrightarrow} Cr _{2} O _{3}+4 H _{2} O + N _{2}\)
(ii) \({NH4NO2 ->[\text{Thermal decomposition}][{\Delta}] 2 H_2O +N2}\)
The number of oxygen atoms present in chemical formula of fuming sulphuric acid is _______.