Question

Which of the following equations is correct for heat of sublimation?

• A. $\Delta_{\text{vap}}H = \Delta_{\text{sub}}H + \Delta_{\text{fus}}H$
• B. $\Delta_{\text{sub}}H = \Delta_{\text{fus}}H - \Delta_{\text{vap}}H$
• C. $\Delta_{\text{fus}}H = \Delta_{\text{sub}}H \times \Delta_{\text{vap}}H$
• D. $\Delta_{\text{sub}}H = \Delta_{\text{fus}}H + \Delta_{\text{vap}}H$

Hint:

Sublimation energy always includes both melting and vaporization energies.

Answer 1

The Correct Option is D

Step 1: Understanding sublimation.
Sublimation is the direct conversion of a solid into vapour without passing through the liquid state.

Step 2: Energy changes involved.
The process of sublimation can be broken into two steps: melting (fusion) followed by vaporization.

Step 3: Mathematical relation.
Therefore, heat of sublimation is equal to the sum of heat of fusion and heat of vaporization.

Step 4: Conclusion.
Hence, the correct relation is $\Delta_{\text{sub}}H = \Delta_{\text{fus}}H + \Delta_{\text{vap}}H$.