20. A 10.0-L flask containing an unknown amount of He, 2.00 mole of Ar, and 3.00
ID: 994687 • Letter: 2
Question
20. A 10.0-L flask containing an unknown amount of He, 2.00 mole of Ar, and 3.00 mole of Ne has a total pressure of 24.5 atm at 25°C. How many moles of He are in the flask?
a. 5.00 mol b. 10.0 mol c. 114 mol d. 119 mol
21. A 10.0-L flask containing 1.00 mole of He, 2.00 mole of Ar, and 3.00 mole of Ne has a total pressure of 24.5 atm at 25°C. What is the partial pressure of Ne in the flask?
a. 4.08 atm b. 8.17 atm c. 12.3 atm d. 24.5 atm
22. What is the root-mean-square (average) speed of a neon atom at 27°C?
a. 5.78 m/s b. 19.3 m/s c. 183 m/s d. 609 m/s
24. Which property of an individual molecule is assumed to be zero in the kinetic-molecular theory?
a. Mass b. Volume c. Speed d. Kinetic Energy
Explanation / Answer
20.
PV = nRT
n = PV/(RT) = 24.5*10/(0.082*(295)) = 10.1281 mol
total mol = 10.1281 = 2 Ar + 3 Ne + He
He = 10.1281 -5 = 5.1281 mol of He
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