1. Gases Practice Problem 1996D Judy Hugh

2. 1996 D Represented above are five identical balloons, each filled to the same volume at 25°C and 1.0 atmosphere pressure with the pure gas indicated. (a) Which balloon contains the greatest mass of gas? Explain. (b) Compare the average kinetic energies of the gas molecules in the balloons. Explain. (c) Which balloon contains the gas that would be expected to deviate most from the behavior of an ideal gas? Explain. (d) Twelve hours after being filled, all the balloons have decreased in size. Predict which balloon will be the smallest. Explain your reasoning.

3. Part a) Answer CO 2 contains the greatest mass of gas because all the balloons contain the same number of molecules, and CO 2 has the greatest molar mass. CO 2 – 44 g/mol O 2 – 32 g/mol He – 4 g/mol N 2 – 28 g/mol CH 4 – 16 g/mol

4. Part b) Answer The average kinetic energies of the gas molecules in the balloons are all equal because they are all held at the same temperature of 25°C Average Kinetic Energy is dependent only on temperature; therefore if the temperature is the same throughout, the average kinetic energies are equal

5. Part c) Answer CO 2 would deviate the most from the behavior of an ideal gas because it has the most electrons, making it have the largest intermolecular (London) forces. It is also the most polarizable because of its geometric configurations.

6. Part d) Answer He would be the smallest balloon after 12 hours have passed because is has the smallest size, it has the greatest molecular speed, and therefore it is then the easiest to penetrate the wall and effuse according to Graham’s Law (click!)Graham’s Law

7. According to Graham's law, the rate at which gases effuse is dependent on their molecular weight Therefore gases with a lower molecular weight will effuse more quickly than gases with a higher molecular weight Thus, lighter molecules will have a higher speed  more molecules will pass through the hole per unit time *This is why a balloon filled with low molecular weight helium will deflate faster than one full of higher molecular weight of: oxygen, nitrogen, methane, or carbon dioxide.

8. FINISHED!