End of Chapter Problems

Test your skills on the following problems.

The Manometer

Example: For image A, the gas container is connected to an open-end U-tube manometer. The mercury in the manometer is 5.0 cm higher on the side open to the atmosphere. If the atmospheric pressure is 759 mmHg, what is the pressure of the gas in atm?

5m

Example: For image B, the gas container is connected to an open-end U-tube manometer. The mercury in the manometer is 7.6 cm lower on the side open to the atmosphere. If the atmospheric pressure is 1080 mmHg, what is the pressure of the gas in atm?

4m

Example: For image C, the gas container is connected to a closed end U-tube manometer. If the pressures of the gas and the atmosphere are initially 800 mmHg and 1200 mmHg respectively, what will be the pressure of the gas if mercury in the manometer is 5.0 cm higher on the side closer to the atmosphere?

2m

The Simple Gas Laws

Example: A sealed container with a moveable piston contains a gas with a pressure of 1380 torr, a volume of 820 mL and a temperature of 31oC. What would the volume be if the new pressure is now 2.83 atm, while the temperature decreased to 25oC?

6m

Example: The pressure in a system is said to be 5.83 atm. What would be the new pressure if the number of moles of gas were quadrupled and the volume were tripled while maintaining constant temperature?

4m

Example: The pressure in a system is said to be 6.11 atm. What would be the new pressure if the number of moles of gas were cut by a third and the volume was cut by a fourth while maintaining constant temperature?

4m

Example: A bicycle tire is filled with air to a pressure of 4.25 atm at a temperature of 19oC. Riding the bike on a hot day increases the temperature of the tire to 52oC. The volume of the tire also increases by 5.0%. What is the new pressure in the bicycle tire?

5m

The Ideal Gas Law

Example: What is the volume, in mL, occupied by 132.7 g CO2 (MW: 44.01 g/mol) at STP?

4m

Example: The volume of O2 gas collected at 24oC and an atmospheric pressure of 702 mmHg is 192 mL. Calculate the mass of the dry oxygen gas collected if the pressure of water vapor at 24oC is 22 mmHg.

5m

Example: What is the density (in g/L) of phosphorus pentachloride at 1157.3 mmHg and 32oC?

4m

Example: A gaseous compound of nitrogen and hydrogen is found to have a density of 0.977 g/L at 528 torr and 100oC. What is the molecular formula of the compound?

a) N2H4            b) NH3          c) HN3         d) HN         e) N4H8

4m

Example: Consider two containers of gases at the same temperature. One has helium at a pressure of 1.00 atm. The other contains carbon dioxide with the same density as the helium gas. What is the pressure of the carbon dioxide gas sample?

a) 0.023 atm         b) 1.00 atm          c) 0.091 atm             d) 0.18 atm          e) 2.12 atm

4m

Example: Determine the molecular formula of a gaseous compound that is 49.48% carbon, 5.19% hydrogen, 28.85% nitrogen, and 16.48% oxygen. At 27oC, the density of the gas is 1.45 g/L and it exerts a pressure of 0.092 atm.

7m

Root Mean Square Speed

Example: Calculate the molar mass, in g/mol, of a gaseous compound with a velocity of 312 m/s at 35oC.

5m

Graham's Law of Effusion

Example: How many times faster will H2 gas pass through a pin hole into an area of vacuum than O2 gas?

a) 32       b) 2        c) 2.5       d) 4         e) 8

3m

Example: Rank the following in order of increasing rate of effusion:

O2            AlF5            CO2             Xe

3m

Kinetic Molecular Theory

Example: Three identical flasks contain equal moles of three different gases all at standard temperature and pressure. Flask A contains C2H4, Flask B contains CO2 and Flask C contains Cl2. Answer each of the following questions:

a) Which flask has the greatest density?

b) Which flask has the most molecules?

c) Which flask contains the most number of atoms?

d) Which flask has the greatest momentum?

7m

Example: Which of the following statements is TRUE?

a) Particles of different masses have the same average speed at a given temperature.

b) The larger a molecule, the faster it will effuse.

c) At very high pressures, a gas will occupy a larger volume than predicted by the ideal gas law.

d) For a given gas, the lower the temperature, the faster it will effuse.

e) None of the above statements are true.

3m

Example: Which conditions of P, T and n make for the most ideal gas?

a) High P, high T, high n

b) Low P, low T, low n

c) Low P, high T, low n

d) Low P, high T, high n

4m

Example: Two identical 10.0 L flasks each containing equal masses of O2 and N2 gas are heated to the same temperature.

Which of the following statements is/are true?

a) The flask with the oxygen gas will have a greater overall pressure.

b) The nitrogen and oxygen gases will have the same average speed or velocity

c) The nitrogen and oxygen gases will have the same average kinetic energy.

3m