Question

Cp of water is 10 J/^oC and that of steam is 15 J/^oC, what is the enthalpy change of water from 75^oC to 110^oC at standard conditions, if the later heat of vaporization of water is 245 J?

(a) 395 J

(b) 645 J

(c) 840 J

(d) 999 J

I have been asked this question in an interview for job.

I'd like to ask this question from Phase Transitions in portion Introduction to Energy Balances for Processes without Reaction and Calculation of Enthalpy Changes of Basic Chemical Engineering

Answer 1

The correct answer is (b) 645 J

To explain I would say: ∆H = 75∫^10010.dT + 245 + 100∫^11015.dT = 25*10 + 245 + 15*10 = 645 J.