Question

What is the final enthalpy of the solution made by mixing 20 grams of solution A having enthalpy 5 J with 5 grams of solution B having enthalpy 10 J?

(a) 2 J

(b) 4 J

(c) 6 J

(d) 7 J

I got this question in exam.

Origin of the question is Effects of Mixing into Energy Balance in division 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

The correct answer is (c) 6 J

To explain I would say: Final enthalpy = 0.8*5 + 0.2*10 = 4 + 2 = 6 J.