What is enthalpy of formation of $$\mathrm{NH}_3$$ if bond enthalpies are as $$(\mathrm{N} \equiv \mathrm{N})=941 \mathrm{~kJ},(\mathrm{H}-\mathrm{H})=436 \mathrm{~kJ},(\mathrm{N}-\mathrm{H})=389 \mathrm{~kJ}$$ ?

What is the difference between $$\Delta H$$ and $$\Delta \mathrm{U}$$ for reaction given below at $$298 \mathrm{~K}$$ ?

($$\mathrm{R}=8.314 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}$$

$$2 \mathrm{C}_6 \mathrm{H}_{6(\ell)}+15 \mathrm{O}_{2(\mathrm{~g})} \rightarrow 12 \mathrm{CO}_{2(\mathrm{~g})}+6 \mathrm{H}_2 \mathrm{O}_{(\ell)}$$

Enthalpy of formation of methane is $$-$$75 kJ/mol. What is the enthalpy change for formation of 24 g of methane?

The expansion of gas having no opposing force is called as