Given: $2Fe + \frac{3}{2} O_2 \to Fe_2O_3$,$\Delta H = -193.4 \ kJ$;
$Mg + \frac{1}{2} O_2 \to MgO$,$\Delta H = -140.2 \ kJ$.
What is the $\Delta H$ of the reaction $3Mg + Fe_2O_3 \to 3MgO + 2Fe$ in $kJ$?

Given that $\Delta H_f(H) = 218 \ kJ/mol$,express the $H-H$ bond energy in $kcal/mol$.

Given $C + O_2 \rightarrow CO_2 + 94.2 \ kcal$,$\Delta H = -94.2 \ kcal$; $H_2 + 1/2 O_2 \rightarrow H_2O + 68.3 \ kcal$,$\Delta H = -68.3 \ kcal$ and $CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O + 210.8 \ kcal$,$\Delta H = -210.8 \ kcal$. Calculate the heat of formation of methane $(CH_4)$ in $kcal$.

Explain the standard enthalpy of combustion $\left( \Delta_{c} H^{\theta} \right)$.

The standard enthalpy of formation of $CO_{(g)}$,$CO_{2(g)}$,$N_2O_{(g)}$ and $N_2O_{4(g)}$ are respectively $-110$,$-393$,$81$ and $-10 \ kJ \ mol^{-1}$. The enthalpy change (in $kJ$) of the following reaction is $N_2O_{4(g)} + 3CO_{(g)} \longrightarrow N_2O_{(g)} + 3CO_{2(g)}$

Heat produced in calories by the combustion of one gram of carbon is called