Question

Enthalpy of sublimation of iodine is ${24 \; cal \; g^{-1}}$ at $200^{\circ}C$. If specific heat of $I_2(s)$ and $I_2(vap)$ are $0.055$ and $0.031\, cal\, g^{-1}K^{-1}$ respectively, then enthalpy of sublimation of iodine at $250^{\circ}C$ in $cal\, g^{-1}$ is :

• A. 2.85
• B. 11.4
• C. 5.7
• D. 22.8

Answer 1

Answer: (D)

22.8

Answer 2

${I_{2(s)} -> I_{2(g)} : \Delta H_1 = 24 \; cal/g \; at \; 200^{\circ} C}$ $\Delta H_2 = \Delta H_1 + \Delta C_{P_{rxn}} (T_2-T_1)$ = $24 + (0.031 -0.055) \times 50$ = $24-1.2$ = $22.8\, Cal/g$