# At 298 K,

Question:

At $298 \mathrm{~K}$, the enthalpy of fusion of a solid $(\mathrm{X})$ is $2.8 \mathrm{~kJ} \mathrm{~mol}^{-1}$ and the enthalpy of vaporisation of the liquid $(\mathrm{X})$ is $98.2 \mathrm{~kJ} \mathrm{~mol}^{-1}$. The enthalpy of sublimation of the substance $(X)$ in $\mathrm{kJ} \mathrm{mol}^{-1}$ is__________ . (in nearest integer)

Solution:

$\Delta \mathrm{H}_{\text {sub }}=\Delta \mathrm{H}_{\text {fus. }}+\Delta \mathrm{H}_{\text {vap. }}$

$=2.8+98.2$

$=101 \mathrm{~kJ} / \mathrm{mol}$