AP Chemistry – Gas Laws Chapter DILL Entries
*In class demonstrations 9/8/2016
1. Hydrogen Balloon:
A hydrogen filled balloon had a volume of 3.75 L at a pressure of 755 mm Hg and temperature of 22.7C and was then combusted in a room
containing oxygen gas. Determine the volume of gaseous water produced when this reaction is complete.
2. Hydrogen and Oxygen Balloon:
A balloon was filled with 1.20L of hydrogen gas and 2.20L of oxygen gas at an atmospheric pressure of 99.8 kPa and temperature of 24.5C and was
then combusted.
(a) Determine the volume of gaseous water produced when this reaction is complete.
(b) Determine the mass of excess reactant left after the combustion reaction.
3.
Extension Question – Related to our in-class discussions of the balloons prior to combustion.
Represented above are five identical rubber balloons, each filled to the same volume at 25C and 1.0 atmosphere pressure with the pure gases
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 particles with the lowest velocity? Explain.
(d) Which balloon contains the gas that would be expected to deviate most from the behavior of an ideal gas? Explain.
(e) The temperature in the room is now decreased to 0C. What should happen to the volume of the balloons and will any of the balloons
change more than another? Explain.
(f) Twelve hours after being filled, all the rubber balloons have decreased in size. Predict which balloon will be the smallest. Explain your
reasoning.
Collection of a Gas over Water
A sample of oxygen gas is collected over water at a pressure of 762 mmHg and a constant temperature of 23.0˚C. In this experiment, 193mL of
oxygen gas is collected and the vapor pressure of water at this temperature is 21.1 mmHg. Determine the mass of oxygen gas collected during this
experiment.
Dalton’s Law and Mole Fractions (Chi)
Use the idea of mole fractions and Dalton’s Law to solve the following problem:
A scuba tank is filled with helium and oxygen gases to a total pressure of 8890 torr. The partial pressure of helium is determined to be 7070 torr.
Calculate the mole fraction of oxygen gas in the cylinder.
Root Mean Square Speed
1. Determine the root mean square velocity of an ammonia molecule at 25.0˚C (Remember that the ‘R’ value needs to have the joule unit so
it is 8.3145 J/K•mol and the joule = kg•m2/s2 so show all units when you calculate this answer…if you end up with m/s then most likely
you have succeeded!)
2.
Now, determine the time it will take for the ammonia molecule to travel from a flask, located 10.0 meters from your nose, to reach you.
3.
[In class demo] Did it take that amount of time to reach your nose? Why or why not?
Effusion and Diffusion
1. Gas X has a molar mass of approximately 72 g/mol and Gas Y has a molar mass of approximately 2 g/mol. How much faster or slower does
Gas Y effuse from a small opening than Gas X at the same temperature?
2.
If you have an unknown gas that effuses at a rate 2 times that of F 2 what is the molar mass of that gas?
3.
The following chemical reaction between two reactant gases occurs. Equimolar amounts of each gas is released from opposite corners of
our laboratory. Relative to each gases starting position, where should they meet in the room and react?
ClNO2(g) + NO(g)
NO2(g) + ClNO(g)