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

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

The standard enthalpy of formation of $NH_3$ is $-46.0 \, kJ \, mol^{-1}$. If the enthalpy of atomization of $H_2$ is $436 \, kJ \, mol^{-1}$ and that of $N_2$ is $712 \, kJ \, mol^{-1}$,what is the average bond enthalpy of the $N-H$ bond in $NH_3$ in $kJ \, mol^{-1}$?

Which of the following has a standard enthalpy of formation equal to zero?

If the enthalpy of formation and enthalpy of solution of $HCl(g)$ are $-92.3 \ kJ/mol$ and $-75.14 \ kJ/mol$ respectively,then find the enthalpy of formation of $Cl^{-}(aq)$. [Assume $\Delta H_{f}(H^{+}) = 0 \ kJ/mol$]

Which of the following compounds has a standard molar enthalpy of formation equal to zero at $298 \ K$?