Question

What is the enthalpy of a mixture having 10% of A with enthalpy 10 J, and 90% of B with enthalpy 20 J?

(a) 10 J

(b) 15 J

(c) 18 J

(d) 19 J

This question was addressed to me at a job interview.

The question is from Heat of Solution, Dissolution and Mixing in chapter Energy Balances that Include the Effects of Chemical Reaction, Ideal Processes, Efficiency and the Mechanical Energy Balance and Heats of Solution and Mixing of Basic Chemical Engineering

Answer 1

Right answer is (d) 19 J

To explain: Heat capacity of mixture = 0.1*10 + 0.9*20 = 19 J.