MSE 345 Spring 2024

MSE 345 Spring 2024
Homework 2:
Due Monday Feb 12th
Question 1: (Lecture 4&5)
Nitrous oxide (N2O) behaves as an ideal gas and has a heat capacity at constant pressure CP = 38.6
J/K∙mol. 4.2 moles of N2O initially at 298 K are heated at constant pressure until a final temperature of
358 K is reached.
(a) Calculate the enthalpy change of N2O during that process.
(b) Calculate the heat transfer Q during that process.
(c) Calculate the work W performed during that process.
(d) Calculate the change in internal energy ΔUduring that process.
Question 2: (Lecture 4&5)
Ar gas behaves as a perfect gas and has a heat capacity at constant volume CV = 2.5∙R J/K∙mol.
(a) Calculate the final pressure when 3 moles of Ar gas initially held at 1.4 atm and 265 K are heated
reversibly to 345 K at constant volume.
(b) Calculate the change in internal energy ΔUduring that process.
(c) Calculate the heat transfer Q during that process.
(d) Calculate the work W performed during that process.
Question 3: (Lecture 4,5,6,7)
3.1 moles of ideal gas undergo an expansion from V1 = 1.2 m3 to V2 =1.7 m3 during an isothermal process
taking place at T = 25°C. Calculate ΔU, ΔH, Q, W when the expansion takes place in the following
conditions: (for a perfect gas U is a function of T only)
(a) A reversible expansion.
(b) A rapid non-reversible expansion against a constant surrounding pressure equal to the final
pressure of the gas.
(c) A free expansion where the gas expands in vacuum against zero external pressure.
Question 4: (Lecture 4&5)
A chlorinated hydrocarbon vapor has a CP which varies with temperature according to CP (J/K∙mol) =
20.17 + 0.3665×T. The vapor behaves as an ideal gas in the range 0°C to 300°C.
(a) Calculate ΔU, ΔH, Q, W when the temperature of 1.00 mole of the gas is raised from 25°C to
200°C reversibly at constant pressure.
(b) Derive ΔU, W, Q when the temperature of 1.00 mole of the gas is raised from 25°C to 200°C
reversibly at constant volume.