$$ \ce{2NO(g) + O2(g)->2NO2(g)} \hspace{5em} \Delta H^{\circ}=\pu{-114.1 kJ} $$
The reaction represented above is one that contributes significantly to the formation of photochemical smog. How much heat is released when \(\pu{120.1 g}\) of \(\ce{NO(g)}\) is converted
to \(\ce{NO2(g)} \)?
The equation tells us that for every \(2\) moles of \(\ce{NO(g)}\), \(\pu{114.1 kJ}\) of heat is released.
$$ \pu{120.1 g }\ce{NO(g)} \cdot \frac{\pu{1 mol }\ce{NO(g)}}{\pu{30 g }\ce{NO(g)}}\cdot \frac{\pu{114.1 kJ}}{\pu{2 mol }\ce{NO(g)}} $$
$$ \approx 120.1\cdot \frac{1}{30}\cdot \frac{114}{2} \pu{kJ} $$
$$ = \boxed{\pu{228 kJ}} $$