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 $kJ$?

If the bond dissociation energies of $XY$,$X_2$,and $Y_2$ (all diatomic molecules) are in the ratio of $1 : 1 : 0.5$ and $\Delta_f H$ for the formation of $XY$ is $-200 \ kJ \ mol^{-1}$,the bond dissociation energy of $X_2$ will be in $kJ \ mol^{-1}$:

The formation of ammonia is shown by the reaction $N_{2(g)} + 3H_{2(g)} \to 2NH_{3(g)}, \Delta_r H^o = -91.8 \, kJ \, mol^{-1}$. What will be the enthalpy of reaction for the decomposition of $NH_3$ according to the reaction $2NH_{3(g)} \to N_{2(g)} + 3H_{2(g)}; \Delta_r H^o = ?$ ..... $kJ \, mol^{-1}$

The heats of formation of $CO_2$ and $H_2O$ are $-97 \, kcal$ and $-68 \, kcal$ respectively. The heat of combustion of benzene is $-783 \, kcal$. What is the heat of formation of benzene in $kcal$?

The enthalpy change of which reaction corresponds to $\Delta H_f^o$ for $Na_2CO_{3(s)}$ at $298 \ K$?

Formation of $NO_{2(g)}$ from $N_{2(g)}$ and $O_{2(g)}$ is an endothermic process. Which of the following is true for this reaction?