Unit 3
Properties of Gases
AP Chemistry Problem Set
Screencast 3-4 Problems
19. Suppose you have two identical 1.0 L sealed containers. Both containers are kept at
exactly 25oC. One vessel contains only neon gas at 1.5 atm, and the other contains only
xenon gas at 2.5 atm.
a. Is the average kinetic energy possessed by the neon atoms greater than, equal to, or
less than that of the xenon atoms? Explain.
b. What variable must be changed in order to decrease the average kinetic energy of the
xenon atoms?
c. Is the root mean square velocity possessed by the neon atoms greater than, equal to,
or less than that of the xenon atoms?
20. Suppose you have two identical 2.0 L cylinders. Both containers are kept at exactly
25oC. One container contains 0.250 moles of helium, and the other contains 0.250 moles
krypton.
a. Find the root mean square velocities of each gas.
Unit 3
Properties of Gases
AP Chemistry Problem Set
b. Explain why these two gases do not share the same average speed under these
conditions.
c. What variable must change in order to increase the average speed of the molecules in
either cylinder? Explain.
21. Find the average kinetic energy per mole of H2(g) molecules at 37oC
22. The average kinetic energy per mole of Cl2(g) is 3.5 KJ/mol in a sealed container. What
is the temperature?
23. Find the molar mass of an unknown gas that has an average root mean square velocity of
343 m/s at 298 K.
Unit 3
Properties of Gases
AP Chemistry Problem Set
24. Which gas from each set will have the highest rate of effusion through a pinhole?
a. Cl2 or F2
b. Xe or Kr
c. N2 or O2
d. Cl2 or Ar
25. Which gaseous isotope from each set will have the highest rate of effusion through a
pinhole?
a.
14
C or
12
C
b. 1H or 2H
c.
3
He or 4He
26. A sealed vessel contains 1.0 mol Ne(g) and 1.0 mol CH4(g). The vessel acquires a leak the
size of a pinhole that allows some gas to escape. What will happen to the ratio moles
Ne(g) /moles CH4(g) in the vessel? Explain.
Unit 3
Properties of Gases
AP Chemistry Problem Set
27. Hydrogen gas, H2(g), diffuses through a pinhole 1.41 times faster than an unknown gas.
a. Find the molar mass of the unknown gas.
b. Identify the unknown gas.
28. Helium diffuses through a pinhole 2.65 times faster than an unknown diatomic gas.
a. Find the molar mass of the unknown gas.
b. Identify the gas.
29.Which gas from the following list effuses about twice as fast as pentane, C 5H12(g)?
O2(g), H2(g), Cl2(g), H2O(g) F2(g)