Question

Enthalpy of sublimation of a substance is equal to

• A. enthalpy of fusion + enthalpy of vapourisation
• B. enthalpy of fusion
• C. enthalpy of vapourisation
• D. twice the enthalpy of vapourisation

Answer 1

Answer: (A)

Solid $\stackrel{\text{Sublimation}}{\to }$ Vapour
This process occurs in two steps,
Step $1$ : Solid $\stackrel{\text{Fusion}}{\to }$ Liquid
Step $2$ : Liquid $\stackrel{\text{Vaporisation}}{\to }$ Vapour
Thus, Enthalpy of sublimation = Enthalpy of fusion + Enthalpy of vaporisation.