Given the following thermochemical equations:
$C_{(s)} + O_{2_{(g)}} \to CO_{2_{(g)}} + 94.2 \, kcal$
$H_{2_{(g)}} + \frac{1}{2} O_{2_{(g)}} \to H_2O_{(l)} + 68.3 \, kcal$
$CH_{4_{(g)}} + 2O_{2_{(g)}} \to CO_{2_{(g)}} + 2H_2O_{(l)} + 210.8 \, kcal$
Calculate the heat of formation of methane in $kcal$.

What will be the standard heat of reaction for the reaction $C_2H_{6(g)} + 7/2 O_{2(g)} \to 2CO_{2(g)} + 3H_2O_{(l)}$ if the standard heat of combustion of $C_{(s)}$ and $H_{2(g)}$ are $-393.5 \ kJ/mol$ and $-285 \ kJ/mol$ respectively,and the standard heat of formation of $C_2H_{6(g)}$ is $-88.2 \ kJ/mol$?

If the standard enthalpies of formation of hydrazine and water are $+50.6 \, kJ/mol$ and $-285.9 \, kJ/mol$ respectively,calculate the $\Delta H$ for the following reaction: $N_2H_{4(g)} + O_{2(g)} \to N_{2(g)} + 2H_2O_{(l)}$ in $kJ \, mol^{-1}$.

Calculate the amount of methane formed by the liberation of $149.6 \ kJ$ of heat using the following equation:
$C_{(s)} + 2H_{2(g)} \longrightarrow CH_{4(g)} \quad \Delta H = -74.8 \ kJ/mol$ (in $g$)

The standard heats of formation for $CH_4$, $C_2H_4$, and $C_3H_8$ are $-17.9$, $12.5$, and $-24.8 \ kcal/mol$ respectively. The heat of reaction $(\Delta H)$ for the reaction $CH_4 + C_2H_4 \rightarrow C_3H_8$ in $kcal$ is:

Calculate $\Delta H^{\circ}$ for the reaction,$Na_2O_{(s)} + SO_{3(g)} \longrightarrow Na_2SO_{4(s)}$ given the following:
$(A) \ Na_{(s)} + H_2O_{(l)} \longrightarrow NaOH_{(s)} + \frac{1}{2} H_{2(g)} \quad \Delta H^{\circ} = -146 \ kJ$
$(B) \ Na_2SO_{4(s)} + H_2O_{(l)} \longrightarrow 2NaOH_{(s)} + SO_{3(g)} \quad \Delta H^{\circ} = +418 \ kJ$
$(C) \ 2Na_2O_{(s)} + 2H_{2(g)} \longrightarrow 4Na_{(s)} + 2H_2O_{(l)} \quad \Delta H^{\circ} = +259 \ kJ$