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Thermodynamics: An Engineering Approach, 4/e

Yunus A. Çengel, University of Nevada, Reno
Michael A. Boles, North Carolina State University

Gas Mixtures

Multiple Choice Quiz

Answer all the questions


1	The composition of a mixture of nitrogen and carbon dioxide gases is 30%-N₂ and 70%-CO₂ by mole fraction. What is the mass fraction of the nitrogen constituent?
		A)	15.2%
		B)	21.4%
		C)	30.2%
		D)	63.7%


2	A mixture of helium and nitrogen is 50%-He and 50%-N₂ by mass analysis. What is the mole fraction of the helium in this mixture?
		A)	39.7%
		B)	43.2%
		C)	67.2%
		D)	87.5%


3	The composition of a gas mixture is 40%-O₂, 40%-N₂, and 20%-He by mass analysis. What is the apparent molecular weight of this mixture?
		A)	6.71 kg/kg-mol
		B)	13.02 kg/kg-mol
		C)	15.70 kg/kg-mol
		D)	18.60 kg/kg-mol


4	The composition of a mixture of gases is 50%-CO₂, 40%-O₂, and 10%-He by volume analysis. What is the apparent molecular weight of this mixture?
		A)	19.3 kg/kg-mol
		B)	24.6 kg/kg-mol
		C)	28.7 kg/kg-mol
		D)	35.2 kg/kg-mol


5	A 1 m³ container contains a mixture of gases composed of 0.02 kg-mol of O₂ and 0.04 kg-mol of He at a pressure of 200 kPa. What is the temperature of this ideal gas mixture?
		A)	300 K
		B)	350 K
		C)	400 K
		D)	450 K


6	A 200 liter container holds 0.5 kg of air and 0.2 kg of helium at a temperature of 350 K. What is the pressure of this ideal gas mixture?
		A)	1.4 MPa
		B)	1.6 MPa
		C)	1.8 MPa
		D)	2.0 MPa


7	A mixture composed of 70%-CO₂ and 30%-He by volume analysis is contained at 1 MPa. What is the partial pressure of the He in this mixture?
		A)	300 kPa
		B)	450 kPa
		C)	600 kPa
		D)	700 kPa


8	A mixture of 30%-Ar and 70%-CO₂ by volume analysis. This mixture is contained in a rigid vessel at 200 kPa, 27 °C. The vessel is now heated until the mixture temperature is 127 °C. Assuming that the specific heats do not change, how much heat was required?
		A)	1.10 MJ/kg-mol
		B)	2.40 MJ/kg-mol
		C)	1.10 MJ/kg
		D)	2.40 MJ/kg


9	A mixture consists of 30%-Ar and 70%-CO₂ by volume analysis. This mixture is contained in a rigid vessel at 200 kPa, 27 ^oC. The vessel is now heated until the mixture temperature is 127 ^oC. Assuming constant specific heats, what is the change in the entropy of the mixture?
		A)	4.780 kJ/kg-mol-K
		B)	6.900 kJ/kg-mol-K
		C)	4.780 kJ/kg-mol-K
		D)	6.900 kJ/kg-mol-K


10	A mixture of 20%-CO₂ and 80%-N₂ by volume is expanded from 1 MPa, 227 °C to 200 kPa as it passes through an adiabatic, steady-flow turbine. Assuming this process is reversible and the specific heats are constant, how much work is produced by this expansion?
		A)	137.9 kJ/kg
		B)	164.5 kJ/kg
		C)	174.3 kJ/kg
		D)	194.2 kJ/kg

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