The value of the enthalpy of neutralization of an acid and a base is significant only when $......$

Enthalpy of formation of $CO_{(g)}$ and $CO_{2(g)}$ are $-110 \ kJ \ mol^{-1}$ and $-393 \ kJ \ mol^{-1}$ respectively. The enthalpy of combustion of $CO$ (in $kJ \ mol^{-1}$) is:

Calculate the standard heat of formation of carbon disulphide $(l)$,given that the standard heat of combustion of carbon $(s)$,sulphur $(s)$ and carbon disulphide $(l)$ are $-393.3, -293.72$ and $-1108.76 \text{ kJ mol}^{-1}$ respectively.

If $H^{+} + OH^{-} \to H_2O + 13.7 \ kcal$,then the heat of neutralization for complete neutralization of one mole of $H_2SO_4$ by base will be.......$kcal$

If $C$ (diamond) $\rightarrow C$ (graphite) $+ X \ kJ \ mol^{-1}$,$C$ (diamond) $+ O_{2(g)} \rightarrow CO_{2(g)} + Y \ kJ \ mol^{-1}$,and $C$ (graphite) $+ O_{2(g)} \rightarrow CO_{2(g)} + Z \ kJ \ mol^{-1}$,at constant temperature,then which of the following relations is correct?

Given $\Delta H_f^{\circ}$ for $CO_{2(g)}$, $CO_{(g)}$ and $H_2 O_{(g)}$ are $-393.5$, $-110.5$ and $-241.8 \ kJ \ mol^{-1}$, respectively. The $\Delta H_r^{\circ}$ [in $kJ \ mol^{-1}$] for the reaction $CO_{2(g)} + H_{2(g)} \longrightarrow CO_{(g)} + H_2 O_{(g)}$ is