What is the heat of atomisation of $P_4O_{6(s)}$?
Given that the heat of sublimation of $P_4O_6$ is $x \ kJ/mol$ and the $P-O$ bond energy is $y \ kJ/mol$.

Enthalpy of formation of $CO_{(g)}$ and $CO_{2(g)}$ are $-110 \ kJ \ mol^{-1}$ and $-393 \ kJ \ mol^{-1}$ respectively. The enthalpy of combustion of $CO$ (in $kJ \ mol^{-1}$) is:

The heat of formation of $CO_{(g)}$ and $CO_{2(g)}$ are $-26.4 \ kcal$ and $-94.0 \ kcal$ respectively. The heat of combustion of carbon monoxide will be $... \ kcal$.

For $NaCl_{(s)}$,the enthalpy of solution is $4 \ kJ \ mol^{-1}$ and the lattice enthalpy is $790 \ kJ \ mol^{-1}$. What is the hydration enthalpy of $NaCl$?

Consider the following reactions:
$(i)$ $H_{(aq)}^{+} + OH^{-}_{(aq)} \longrightarrow H_2O_{(l)}$,$\Delta H = -X_1 \ kJ \ mol^{-1}$
$(ii)$ $H_{2_{(g)}} + \frac{1}{2} O_{2_{(g)}} \longrightarrow H_2O_{(l)}$,$\Delta H = -X_2 \ kJ \ mol^{-1}$
$(iii)$ $CO_{2_{(g)}} + H_{2_{(g)}} \longrightarrow CO_{(g)} + H_2O_{(l)}$,$\Delta H = -X_3 \ kJ \ mol^{-1}$
$(iv)$ $C_2H_{2_{(g)}} + \frac{5}{2} O_{2_{(g)}} \longrightarrow 2CO_{2_{(g)}} + H_2O_{(l)}$,$\Delta H = -X_4 \ kJ \ mol^{-1}$
Enthalpy of formation of $H_2O_{(l)}$ is

Calculate the enthalpy change for the following reaction:
$H_2C=CH_{2(g)} + H_{2(g)} \longrightarrow H_3C-CH_{3(g)}$
[The bond energies of $C-H, C-C, C=C$ and $H-H$ are $414, 347, 615$ and $435 \ kJ/mol$ respectively.] (in $kJ$)