The heat of combustion of a substance is:

Assertion $(A)$: Formation of $H_2O_{(\ell)}$ from $H_{2(g)}$ and $O_{2(g)}$ is more exothermic than formation of $H_2O_{(g)}$ from $H_{2(g)}$ and $O_{2(g)}$.
Reason $(R)$: $H_2O_{(\ell)}$ has more attraction force than $H_2O_{(g)}$ and it is more stable than $H_2O_{(g)}$.

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 enthalpy of formation of carbon monoxide $(CO).$ Given: $C_{(s)} + O_{2(g)} \rightarrow CO_{2(g)}, \Delta H = -393.3 \ kJ \ mol^{-1}$ and $CO_{(g)} + \frac{1}{2} O_{2(g)} \rightarrow CO_{2(g)}, \Delta H = -282.2 \ kJ \ mol^{-1}.$

Given that the bond energies of $N \equiv N$ is $946 \ kJ \ mol^{-1}$,$H-H$ is $435 \ kJ \ mol^{-1}$,$N-N$ is $159 \ kJ \ mol^{-1}$,and $N-H$ is $389 \ kJ \ mol^{-1}$,calculate the enthalpy of formation for the gas phase reaction $N_2 + 2H_2 \rightarrow N_2H_4$ in $kJ \ mol^{-1}$.

The enthalpy of neutralization of a strong acid by a strong base is $-57.32 \ kJ/mol$. The enthalpy of formation of water is $-285.84 \ kJ/mol$. The enthalpy of formation of hydroxyl ion is......$kJ/mol$. (Assume $\Delta H_{f}^{\circ}(H^{+}_{(aq)}) = 0 \ kJ/mol$)