Paper 1 May/June 2011 CHEMISTRY (9701/11) IGCSE

Nitrogen monoxide is rapidly oxidised to nitrogen dioxide.
$2NO\left( g \right) + {O_2}\left( g \right) \to 2N{O_2}\left( g \right){\text{ }}$
Nitrogen dioxide can then dimerise to form dinitrogen tetroxide.
$2N{O_2}\left( g \right){N_2}{O_4}\left( g \right)\,\,\,\,\,\Delta {H^o} = -58kJ\,mo{l^{-1}}{\text{ }}$
$\Delta H_f^oNO = + 91kJ\,mo{l^{-1}}\,and{\text{ }}\Delta H_f^oN{O_2} = + 34kJ\,mo{l^{-1}}$
What…