Question

the standard heat of formation of NO2 and N2O4 are 8and 4 kcal/ mol respectively the heat of dimerisation of NO2 in kcal is

Answer 1

The reaction of dimerisation of NO2 is the reaction of nitrogen dioxide with itself to produce dinitrogen tetraoxygen as follows:

kjj$2 NO_2  > N_2O_4$

Heat of dimerisation is the change in heat of formation of product and heat of formation of reactant as follows:

heat of formation of $H_N_2_O_4 = 4 kcal /mol</p><p>heat of formation of H_N_O_2$ = 8 kcal /mol

heat of dimerisation = $H_N_2_O_4 -  2 x H_N_O_2$

$= 4 -  2 X 8= 4 - 16 = -12$ kcal /mol

Thus, heat of dimerisation of NO2 is - 12 kcal /mol