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

From the following data,the enthalpy of vaporization of liquid water in $KJ \, mol^{-1}$ will be:
$H_2(g) + 1/2 O_2(g) \rightarrow H_2O(l); \Delta H = -285.77 \, KJ \, mol^{-1}$
$H_2(g) + 1/2 O_2(g) \rightarrow H_2O(g); \Delta H = -241.84 \, KJ \, mol^{-1}$

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

The heat of neutralisation of a strong acid and a strong alkali is $57.0 \ kJ \ mol^{-1}$. The heat released when $0.5 \ mol$ of $HNO_3$ solution is mixed with $0.2 \ mol$ of $KOH$ is: (in $kJ$)

When it is not possible to calculate the enthalpy of a reaction experimentally,it can be calculated by .....

The enthalpy change $(\Delta H)$ for the process $N_2H_{4(g)} \to 2N_{(g)} + 4H_{(g)}$ is $1724 \ kJ \ mol^{-1}$. If the bond energy of $N-H$ bond in ammonia is $391 \ kJ \ mol^{-1}$,what is the bond energy of $N-N$ bond in $N_2H_4$ in $kJ \ mol^{-1}$?