From the following thermochemical equations,find out the heat of ionisation $Z$ for a weak acid $HA$:
$HA \to A^{-} + H^{+} , \Delta H = Z$
$H^{+} + OH^{-} \to H_2O , \Delta H = X$
$HA + OH^{-} \to A^{-} + H_2O , \Delta H = Y$

If the ratio of the enthalpy of formation of $CO_2$ and $SO_2$ is $4:3$ and the enthalpy of formation of $CS_2$ is $26 \ kcal/mol$,then what will be the enthalpy of formation of $SO_2(g)$ based on the following reaction?
$CS_2(l) + 3O_2(g) \to CO_2(g) + 2SO_2(g)$

The average $S-F$ bond energy in $kJ \ mol^{-1}$ of $SF_{6}$ is $......$ . (Rounded off to the nearest integer) [Given : The values of standard enthalpy of formation of $SF_{6(g)}$,$S_{(g)}$ and $F_{(g)}$ are $-1100$,$275$ and $80 \ kJ \ mol^{-1}$ respectively.]

The enthalpy of formation of $NH_3$ is $-46 \ kJ \ mol^{-1}$. The enthalpy change for the reaction $2 NH_{3(g)} \longrightarrow N_{2(g)} + 3 H_{2(g)}$ is

The bond enthalpies of $H_2$,$X_2$,and $HX$ are in the ratio of $2 : 1 : 2$. If the standard enthalpy of formation of $HX$ is $-50 \ kJ \ mol^{-1}$,the bond enthalpy of $H_2$ is .... $kJ \ mol^{-1}$.

At $25^{\circ}C$,the heats of combustion for $CH_{4(g)}$,$C_{(s)}$,and $H_{2(g)}$ are $-212.4 \, kcal$,$-94.0 \, kcal$,and $-68.4 \, kcal$ respectively. The heat of formation for $CH_{4(g)}$ in $kcal$ is: