Question

What is the change in internal energy of 1 mole of air ((Cv = 2.1 X 10^4  J/mole^oC), if its temperature changes from 10^oC to 5^oC?

(a) 84 kJ

(b) 105 kJ

(c) – 84 kJ

(d) – 105 kJ

This question was addressed to me in a national level competition.

Question is from Internal Energy and Energy Conversion Concept in chapter Introduction to Energy Balances for Processes without Reaction and Calculation of Enthalpy Changes of Basic Chemical Engineering

Answer 1

Correct option is (d) – 105 kJ

To explain: Change in internal energy = 1*(2.1 X 104)*(5 – 10) = – 105 kJ.