Quiz on Gases

Problem #1: What is the correct way of explaining how a vacuum cleaner works? (A or B?)

A) The spinning motor creates a partial vacuum which creates a suction effect and draws the dirt into the vacuum cleaner.
B) The spinning motor pushes air out of the vacuum cleaner reducing the number of collisions of air inside. The outside air molecules then collide more often which causes the air to rush in knocking dirt in as it goes.

Problem #2: One morning your co-workers and you blow up about a hundred balloons with helium. You tie them together and left them all floating near the ceiling. A few hours later you peek through a window to the room and see all of them on the floor. They still look just as inflated as they did when they were blown up (no helium leaked out). You tell the coworkers not to go into the room and for sure do not light a match. The company you work at develops fuel cells. Why did the helium filled balloons fall to the ground?

The warnings on all spray cans will say something like this: "Contents under pressure. Do not puncture, incinerate, or expose to temperature above 120F. Heat from sunlight, radiators, stoves, hot water, and other heat sources could cause container to burst." Problem 3: Going from 100°F(311K) to 150F(338K) is only a 8% increase of temperature and also only a 8% increase in pressure if the container holds only gas. However, some left over paint in the can will cause the pressure to go much higher. Why is that?
Problem 4: 520 gas cylinders containing 300,000 pounds of chlorine gas was used as a chemical weapon at Ypres, France in 1915. 5,000 soldiers died and 15,000 injured. 4a) Air weighs 28.8 grams per mole. How many grams per mole does chlorine gas (Cl₂) weigh? 4b) Will chlorine gas stay close to the ground or rise up into the air? 4c) How many grams is 300,000 lbs mentioned above, knowing that 1 lb = 454 grams. 4d) How many moles of Cl₂ is 300,000 lbs of Cl₂? (use grams from 4c).
Problem 5: On the right is an oxygen concentrator. It takes rooms air and filters out the nitrogen gas leaving pure oxygen gas for a patient to breathe. It starts by taking room air and pressurizing it. The pressurized gas is then passed through filters that let oxygen atoms pass but not nitrogen. Pressure is achieved with a pump. A piston starts 3 inches from the top of the cylinder and ends 1 inch from the top. If the pressure at 3 inches is 15 psi, what is the pressure at 1 inch?
The results of a basketball game was called into question with allegations of the basketball being filled with a gas other than air. Your task is to investigate. The ideal gas law PV=nRT may help with some rearranging. Divide both sides by n gives PV/n=RT, now divide both sides by PV to get 1/n=RT/PV. Now multiply by both sides by grams to get g/n=gRT/PV. "g/n" is grams per mole and that is what the Periodic Table lists for each element (atomic mass). So the final formula would read: Atomic wt=gRT/PV Calculate gRT/PV and match it to the element that has that atomic mass. To calculate you need g, T, P, & V. You measured the radius as 12.4 cm. Using formula for sphere V= ⁴/₃ x pi x r³, you calculate its volume as 8,000. mL. The pressure is 29.4 psi and the temperature is 81°F (27°C,300K) You weigh the basketball and it weighs 600.65 g. You let out the gas and find the empty weight as 600.00g. Problem 6: What is the gas they put in the basketball? (Hint: turn 29.4 psi to Atm (14.7psi=1atm), convert 8,000mL to liters, use Kelvin, and use 0.0821 for R).
For students in my CHM130 class, send answers to chm130@chemistryland.com. Use a subject line of "Quiz on Gases"

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Since Apr 27, 2008