Workshop: Gas Laws and Applications
1. What gases make up the earth’s atmosphere?
2. Assume that air is 80% N2 and 20% O2. What is the average molar mass of air? Show your calculaltion.
3. An average pair of human lungs contains about 3.5 L of air after inhalation and about 3.0 L after exhalation. Assuming that air in your lungs is at 37°C and 1.0 atm, determine a) the number of moles and b) the mass of air in a typical breath.
4. A balloon is filled with helium gas at 27°C and 1.00 atm pressure. As the balloon rises, the volume of the balloon increases by a factor of 1.60 and the temperature decreases to 15°C. Assuming that no helium escapes from the balloon, what is the final pressure?
5. The volume of one mole of gaseous nitrogen at standard temperature and pressure is 22.4 L. The density of liquid nitrogen at –196°C is 0.808 g/mL. What is the volume of one mole of liquid nitrogen? (Be CAREFUL with your assumptions.)
6. A gas is known to be one of the following nitrogen oxides: NO, NO2, N2O4, or N2O. It has a density of 1.96 g/L at 273 K and 1.00 atm. Determine its identity. Show your calculation.
7. Consider the following description of an automobile air bag:
“In a frontal impact of sufficient severity, the air bag sensing system on the vehicle will detect that the vehicle is suddenly stopping as a result of a the crash. The sensing system completes an electrical circuit, triggering a chemical reaction of the sodium azide sealed in the inflators. The reaction produces nitrogen gas, which inflates the air bag.” (Source: 1995 Saturn Owner’s Manual, p. 33). The reaction that occurs is
2 NaN3 (s) -> 2 Na (s) + 3 N2 (g)
How many grams of sodium azide are needed to produce 40.0 L of nitrogen to fill an air bag at a pressure of 1.30 atm and a temperature of 28.0°C?
8. The graphs on the following page show how certain properties of the atmosphere vary with altitude (the distance above the earth’s surface). Figure 1 shows how the average temperature changes with altitude. Figure 2 shows how atmospheric pressure changes with altitude. Figure 3 shows how the molar mass of air changes with altitude. Use the graphs and your knowledge of the ideal gas law to calculate the density of air at altitudes of 5 km and 10 km.