If the $\Delta H_{fusion}$ of a substance is $'x'$ and $\Delta H_{vap}$ is $'y'$,then $\Delta H_{sublimation}$ will be:

What is the heat of formation of $HCl_{(g)}$ from the following equation (in $kJ$)?
$H_{2(g)} + Cl_{2(g)} \rightarrow 2HCl_{(g)} \quad \Delta_{r}H = -194 \ kJ$

Which of the following values of heat of formation indicates that the product is least stable in $kcal$?

The enthalpy change at $298 \ K$ for the decomposition of water is given in the following two steps:
Step $I$: $H_2O_{(g)} \to H_{(g)} + OH_{(g)}$; $\Delta H = 498 \ kJ \ mol^{-1}$
Step $II$: $OH_{(g)} \to H_{(g)} + O_{(g)}$; $\Delta H = 428 \ kJ \ mol^{-1}$
The average bond enthalpy of the $O-H$ bond is $.... \ kJ \ mol^{-1}$

For the reaction $N_2 + 3 X_2 \longrightarrow 2 NX_3$,where $X = F, Cl$ (the average bond energies are $F-F = 155 \ kJ \ mol^{-1}$,$N-F = 272 \ kJ \ mol^{-1}$,$Cl-Cl = 242 \ kJ \ mol^{-1}$,$N-Cl = 200 \ kJ \ mol^{-1}$ and $N \equiv N = 941 \ kJ \ mol^{-1}$),the heats of formation of $NF_3$ and $NCl_3$ in $kJ \ mol^{-1}$,respectively,are closest to

The enthalpy of neutralization of any strong acid and strong base is constant because......