$C + \frac{1}{2} O_2 \to CO; \Delta H = -42 \ kJ$
$CO + \frac{1}{2} O_2 \to CO_2; \Delta H = -24 \ kJ$
The heat of formation of $CO_2$ is ..... $kJ$.

The conversion of oxygen to ozone represented by the equation $3O_2 \to 2O_3$ is an endothermic reaction. The enthalpy change $\Delta H$ accompanying the reaction:

The enthalpy of neutralization of $NH_4OH$ with $HCl$ is $-51.40 \, kJ/equiv$. The enthalpy of dissociation of $NH_4OH$ is ..... $kJ$.

Combustion of $1$ $mol$ of benzene is expressed as:
$C_6H_{6(l)} + \frac{15}{2} O_{2(g)} \rightarrow 6CO_{2(g)} + 3H_2O_{(l)}$
The standard enthalpy of combustion of $2$ $mol$ of benzene is $-x$ $kJ$.
$x = . . . . . . . . . .$
$(1)$ Standard enthalpy of formation of $1$ $mol$ of $C_6H_{6(l)}$ is $48.5$ $kJ \ mol^{-1}$.
$(2)$ Standard enthalpy of formation of $1$ $mol$ of $CO_{2(g)}$ is $-393.5$ $kJ \ mol^{-1}$.
$(3)$ Standard enthalpy of formation of $1$ $mol$ of $H_2O_{(l)}$ is $-286$ $kJ \ mol^{-1}$.

Based on Hess's law calculations,what is the average $S-O$ bond energy in $SO_3$ if $\Delta H_f^o$ of $SO_3$ is $-270 \ kJ \ mol^{-1}$. Given: Bond energy of $O=O$ is $495 \ kJ \ mol^{-1}$,heat of sublimation for $S_{(s)}$ is $277 \ kJ \ mol^{-1}$,and bond energy of $S=O$ is not provided,but we assume the formation reaction: $S_{(s)} + \frac{3}{2} O_{2(g)} \rightarrow SO_{3(g)}$. Use the atomization energy of $S_{(s)} = 277 \ kJ \ mol^{-1}$ and $O=O = 495 \ kJ \ mol^{-1}$. Calculate the average $S-O$ bond energy in $SO_3$.

Among the following given substances,the one with zero $\Delta_{f}H^{\circ}$ is