$H_{2(g)} + \frac{1}{2}O_{2(g)} \to H_2O_{(l)}$; $\Delta H$ at $298 \ K = -285.8 \ kJ$. The molar enthalpy of vaporization of water at $1 \ atm$ and $25^{\circ}C$ is $44 \ kJ$. The standard enthalpy of formation of $1 \ mole$ of water vapor at $25^{\circ}C$ is $...... \ kJ$. (in $.8$)

Given that $:$
$2 C_{(s)} + 2 O_{2_{(g)}} \rightarrow 2 CO_{2_{(g)}} ; \Delta H = -787 \ kJ$
$H_{2_{(g)}} + \frac{1}{2} O_{2_{(g)}} \rightarrow H_2 O_{(l)} ; \Delta H = -286 \ kJ$
$C_2 H_{2_{(g)}} + \frac{5}{2} O_{2_{(g)}} \rightarrow 2 CO_{2_{(g)}} + H_2 O_{(l)} ; \Delta H = -1301 \ kJ$
The heat of formation of acetylene will be $:-$

$C + 2S \rightarrow CS_2$; $\Delta H^o = +117 \, kJ \, mol^{-1}$; $C + O_2 \rightarrow CO_2$; $\Delta H^o = -393 \, kJ \, mol^{-1}$; $S + O_2 \rightarrow SO_2$; $\Delta H^o = -297 \, kJ \, mol^{-1}$. The heat of combustion of $CS_2$ in $kJ \, mol^{-1}$ is:

For strong acid and strong base neutralisation,the net chemical change is $H^{+} + OH^{-} \longrightarrow H_2O_{(l)}$; $\Delta_r H^{\circ} = -55.84 \ kJ \ mol^{-1}$. If the enthalpy of neutralisation of $CH_3COOH$ by $NaOH$ is $-49.86 \ kJ \ mol^{-1}$,then the enthalpy of ionisation of $CH_3COOH$ is:

Which among the following represents the reaction of formation of the product?

Given that $C_{(g)} + 4H_{(g)} \longrightarrow CH_{4(g)}$,$\Delta H^{\circ} = -1665 \ kJ$. What is the bond energy per mole of $C-H$ bond?