Q. Ice at $-5^\circ$C is heated to become vapor with temperature of $110^\circ$C at atmospheric pressure. The entropy change associated with this process can be obtained from
A) [image:2025J23S1_Q64_opt_a.png]
B) [image:2025J23S1_Q64_opt_b.png]
C) [image:2025J23S1_Q64_opt_c.png]
D) [image:2025J23S1_Q64_opt_d.png]
Explanation
[Solution by Dr. Abubacker] Entropy changes add stage by stage: heating ice $\int\frac{C_p}{T}dT$ (268→273 K), fusion $\frac{\Delta H_{fus}}{T_f}$, heating water $\int\frac{C_p}TdT$ (273→373 K), vaporisation $\frac{\Delta H_{vap}}{T_b}$ and heating vapour $\int\frac{C_p}TdT$ (373→383 K). Only option (2) has $C_p/T$ inside every integral. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.