Question:

Enthalpy of sublimation of iodine is 24 cal/g at 200°C. If specific heat of I₂(s) and I₂(vap) are 0.055 and 0.031 cal/g⁻¹K⁻¹ respectively, then enthalpy of sublimation of iodine at 250°C in cal/g is:

2.85

5.7

22.8

11.4

Correct option is D. 22.8
I₂(s) → I₂(g): ΔH₁ = 24 cal/g at 200°C
ΔH₂ = ΔH₁ + ΔCp(T₂ - T₁)
= 24 + (0.031 - 0.055) × 50
= 24 - 1.2
= 22.8 cal/g