Average bond enthalpy of water is $464.5 \text{ kJ mol}^{-1}$. If the energy required to break the first $O-H$ bond is $502 \text{ kJ mol}^{-1}$,how much energy per mol is required to break the second $O-H$ bond?

If $C_{(s)} + O_{2(g)} \longrightarrow CO_{2(g)}; \Delta H = r$ and $CO_{(g)} + \frac{1}{2} O_{2(g)} \longrightarrow CO_{2(g)}; \Delta H = s$,then the heat of formation of $CO$ is

Given the bond energies of $N \equiv N$,$H - H$ and $N - H$ bonds are $945$,$436$ and $391 \ kJ \cdot mol^{-1}$ respectively,the enthalpy of the following reaction $N_{2(g)} + 3H_{2(g)} \to 2NH_{3(g)}$ is ...... $kJ$.

The standard enthalpies of formation of $Al_{2}O_{3}$ and $CaO$ are $-1675 \ kJ \ mol^{-1}$ and $-635 \ kJ \ mol^{-1}$ respectively.
For the reaction $3 CaO + 2 Al \rightarrow 3 Ca + Al_{2}O_{3}$,the standard reaction enthalpy $\Delta_{r}H^{\circ}$ is .......... $kJ$.
(Round off to the Nearest Integer).

If for the reaction $CCl_{4(g)} \rightarrow C_{(g)} + 4Cl_{(g)}$ the following data is given:
$\Delta_{vap} H^{\theta} (CCl_{4(l)}) = 30 \ kJ \ mol^{-1}$
$\Delta_{f} H^{\theta} (CCl_{4(l)}) = -136.0 \ kJ \ mol^{-1}$
$\Delta_{a} H^{\theta} (C_{(s)}) = 714.0 \ kJ \ mol^{-1}$
$\Delta_{a} H^{\theta} (Cl_{2(g)}) = 242.0 \ kJ \ mol^{-1}$
Calculate the mean bond enthalpy of $C-Cl$ in $CCl_{4(g)}$.

Energy required to dissociate $16 \ g$ of $O_{2(g)}$ into free atoms is $x \ kJ$. The value of bond enthalpy of $O=O$ bond is