Compounds with high heat of formation are less stable because

The bond dissociation enthalpies of $H_2$, $Cl_2$, and $HCl$ are $434 \text{ kJ mol}^{-1}$, $242 \text{ kJ mol}^{-1}$, and $431 \text{ kJ mol}^{-1}$ respectively. Calculate the enthalpy of formation of $HCl$.

Calculate the enthalpy of vaporisation of ethanol if $11.5 \ g$ of ethanol is completely vaporised by supplying $11.8 \ kJ$ of heat.

The energy absorbed by each molecule $(A_2)$ of a substance is $4.4 \times 10^{-19} \ J$ and bond energy per molecule is $4.0 \times 10^{-19} \ J.$ The kinetic energy of the molecule per atom will be $...... \times 10^{-20} \ J$

If the standard heat of the reaction $Fe_2O_{3(s)} + 3CO_{(g)} = 2Fe_{(s)} + 3CO_{2(g)}$ is $-6.6 \, kcal$,then $\Delta H_f^o$ for $Fe_2O_{3(s)}$ is $...... \, kcal/mol$. [Given: $\Delta H_f^o$ of $CO_{(g)} = -26.4 \, kcal$ and $\Delta H_f^o$ of $CO_{2(g)} = -94 \, kcal$]

Hess's law is based on