Enthalpy Change, ∆ᵣH of a Reaction – Reaction Enthalpy

Calculate the enthalpy change for the process
${\mathrm{CCl}}_4\left(\mathrm{g}\right)\to \mathrm{C}\left(\mathrm{g}\right) + 4 \mathrm{Cl}\left(\mathrm{g}\right)$
and calculate bond enthalpy of $\mathrm{C} – \mathrm{Cl}$ in ${\mathrm{CCl}}_4\left(\mathrm{g}\right)$.
${∆}_{\mathrm{vap}}\mathrm{H}°\left({\mathrm{CCl}}_4\right) = 30.5 \mathrm{kJ} {\mathrm{mol}}^{–1}.$
${∆}_{\mathrm{f}}\mathrm{H}°\left({\mathrm{CCl}}_4\right) = –135.5 \mathrm{kJ} {\mathrm{mol}}^{–1}.$
${∆}_{\mathrm{a}}\mathrm{H}° \left(\mathrm{C}\right) = 715.0 \mathrm{kJ} {\mathrm{mol}}^{–1}$ , where ${∆}_{\mathrm{a}}\mathrm{H}°$is enthalpy of atomisation
${∆}_{\mathrm{a}}\mathrm{H}°\left({\mathrm{Cl}}_2\right) = 242 \mathrm{kJ} {\mathrm{mol}}^{–1}$

Given

${\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\to 2{\mathrm{NH}}_3\left(\mathrm{g}\right) ; {∆}_{\mathrm{r}}\mathrm{H}°=-92.4 \mathrm{kJ} {\mathrm{mol}}^{-1}$ 

What is the standard enthalpy of formation of ${\mathrm{NH}}_3$ gas?

The reaction of cyanamide,${\mathrm{NH}}_2\mathrm{CN} \left(\mathrm{s}\right)$, with dioxygen was carried out in a bomb calorimeter and $∆\mathrm{U}$ was found to be $-742.7 \mathrm{kJ} {\mathrm{mol}}^{-1}$ at  $298 \mathrm{K}$. Calculate the enthalpy change for the reaction at $298 \mathrm{K}$.
${\mathrm{NH}}_2\mathrm{CN}\left(\mathrm{g}\right)+\frac{3}{2}{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{N}}_2\left(\mathrm{g}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

The enthalpy of combustion of methane, graphite and dihydrogen at $298 \mathrm{K}$ are, $-890.3\mathrm{kJ} {\mathrm{mol}}^{-1}-393.5\mathrm{kJ} {\mathrm{mol}}^{-1},$ and $-285.8\mathrm{kJ} {\mathrm{mol}}^{-1}$ respectively. Enthalpy of formation of ${\mathrm{CH}}_4\left(\mathrm{g}\right)$ will be

$∆{\mathrm{U}}^{\ominus }$ of combustion of methane is $-\mathrm{X} {\mathrm{kJmol}}^{-1}$. The value of $∆{\mathrm{H}}^{\ominus }$ is

The enthalpies of all elements in their standard states are: