The bond dissociation energies of gaseous $H_2$,$Cl_2$ and $HCl$ are $104$,$58$ and $103 \ kcal$ respectively. The enthalpy of formation of $HCl$ gas would be $... \ kcal$.

At $298 \ K$ and constant pressure, the heat of formation of $C_2H_{2(g)}$ and $C_6H_{6(g)}$ is $230 \ kJ \ mol^{-1}$ and $85 \ kJ \ mol^{-1}$ respectively. What will be the change in heat for the reaction?
$3 \ C_2H_{2(g)} \rightarrow C_6H_{6(g)}$

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

The heat of combustion of solid benzoic acid at constant volume is $-321.30 \ kJ$ at $27^{\circ} C$. The heat of combustion at constant pressure is $(-321.30 - x R) \ kJ$. The value of $x$ is . . . . . . .

Hess's law is based on

The $\Delta H^o_f$ for $CO_{2(g)}$,$CO_{(g)}$,and $H_2O_{(g)}$ are $-393.5$,$-110.5$,and $-241.8 \ kJ/mol$ respectively. The standard enthalpy change (in $kJ$) for the reaction $CO_{2(g)} + H_{2(g)} \to CO_{(g)} + H_2O_{(g)}$ is: