Name: ________________________
Hour: ____ Date: ___________
AP Chemistry: 10HW
Directions: Complete the following problems.
1A. Calculate the pressure of the gas in the flask of the open-end manometer, in torr.
1B. Mercury’s density is 13.6 g/mL. Now assume that the manometer shown above contains an oil of density
1.38 g/mL instead of mercury. Find the pressure of the gas in the flask, in torr.
2A. Assuming no temperature change, a 3.25-L helium balloon at sea level will have what volume when the
confining pressure on it drops to 450. torr?
2B. A gas sample occupies 418 mL at 25oC. If pressure remains constant, what volume does it occupy at
50.oC?
3A. A gas is in a 350.-mL cylinder at 23oC and 715 mm Hg. What is the new pressure of the gas if it is
compressed down to 35 mL and its temperature rises to 458oC?
3B. A sample of carbon monoxide occupies 32.6 L at 45oC and 157.4 kPa. What is its volume at STP?
4A. Two 80.0-L gas tanks must be filled: one with helium, the other with hydrogen. What mass of each gas is
needed at 23oC to produce a pressure of 1535 torr in each tank?
ANSWERS:
1A. 642 torr
1B. 748 torr
2A. 5.49 L
2B. 453 mL
3A. 1.8 x 104 mm Hg
3B. 43.5 L
4A. 26.6 g He
13.3 g H2
4B. A 2.50-L metal can that is able to withstand an internal pressure of 7.11 atm is filled with nitrogen at sea
level and 29oC. Find the absolute temperature at which the can will burst.
5. An 11.2-L sample of argon is determined to contain 0.450 mol of gas. At the same temperature and pressure,
how many moles of nitrogen would there be in a 29.4-L sample of nitrogen?
6A. An unknown diatomic gas has a density of 1.696 g/L at STP. Identify the gas.
6B. A 320-mL flask at 373 K and 600. torr contains 1.20 g of a gaseous compound having an empirical formula
of CHCl. Determine the compound’s molecular formula.
6C. Determine the density of uranium hexafluoride gas at 60.oC and 745 mm Hg.
6D. The atmosphere is 78% nitrogen, 21% oxygen, and 1.0% argon. Find the atmosphere’s density at STP.
ANSWERS:
4B. 2150 K
5. 1.18 mol
6A. F2
6B. C3H3Cl3
6C. 12.6 g/L
6D. 1.3 g/L
7A. Hydrogen peroxide decomposes into water vapor and oxygen. Suppose you have 225 g of a solution that is
50% hydrogen peroxide by mass. What volume of oxygen can be produced at 25oC and 792 torr?
7B. Sulfur trioxide can be produced in a two-step reaction:
S8 + 8 O2  8 SO2
2 SO2 + O2  2 SO3
What volume of oxygen, at 385oC and 4.65 atm, is
needed to convert 25.0 g of sulfur into sulfur trioxide?
8A. Upon ignition, methanol (CH3OH) burns readily in air. How many total moles of products are formed if
60.0 mL of methanol (D = 0.850 g/mL) react with 18.7 L of oxygen at 37oC and 1.72 atm?
ANSWERS:
7A. 38.8 L
7B. 13.6 L
8A. 2.53 mol products
8B. Ammonia and carbon dioxide gases react to produce urea (H2NCONH2) and water. Ammonia at 228oC and
80. atm flows into a reactor at a rate of 500. L/min. Carbon dioxide at 228oC and 40. atm flows in at a
rate of 600. L/min. How many kg of urea are produced per minute, with a 72% yield?
9A. A 9.8-g piece of solid carbon dioxide is placed into an otherwise empty 3.0-L container. What is the pressure
(in atm) in the container when the carbon dioxide vaporizes, assuming the final temperature is 33oC?
9B. If the piece of carbon dioxide above were placed in the same container – which already held air at 720 torr –
find the CO2’s partial pressure AND the total pressure in the container after the CO2 sublimed. Use atm.
10A. A 4.00-g, 50/50-by-mass mixture of hydrogen and helium is placed in a 5.00-L container at 21oC. Using
atm, find the partial pressure of each gas and the total pressure in the container.
10B. A 1.00-L sample of 50/50-by-mass mixture of helium and xenon is at 120.oC and 800. Torr. What are the
partial pressures of the individual gases?
ANSWERS:
8B. 21 kg/min
9A. 1.9 atm
9B. 1.9 atm; 2.8 atm
10A. PH2 = 4.83 atm, PHe = 2.41 atm, Ptot = 7.24 atm
10B. PXe = 24 torr, PHe = 776 torr
11A. When a sample of zinc reacted with excess hydrochloric acid, 340. mL of hydrogen were collected over
water at 30.oC. If the atmospheric pressure was 0.963 atm and the vapor pressure of water at 30.oC is
32 torr, find the mass of zinc that was consumed.
11B. Potassium chlorate decomposes into potassium chloride and oxygen upon heating. A 0.7811-g mixture
contains an unknown amount of potassium chlorate. When the mixture is heated, 47.2 mL of oxygen are
collected over water at 22oC and 714 torr. What mass percent of the mixture was potassium chlorate?
The vapor pressure of water at 22oC is 19.8 torr.
12A. Assuming uniform temperature, do all atoms in a given sample of neon have the same kinetic energy?
12B. Does a 1-mol sample of Ar have the same total KE as a 1-mol sample of Rn, at a given temperature?
13A. Calculate the rms speed of nitrogen dioxide at 85oC.
13B. Calculate the rms speed of nitrogen at –75oC.
ANSWERS:
11A. 0.824 g
11B. 18.6%
13A. 441 m/s
13B. 420. m/s
14A. Calculate the average kinetic energy of a nitrogen dioxide molecule at 85oC.
14B. Calculate the average kinetic energy of a nitrogen molecule at –75oC.
15. A rigid container has a mixture of carbon dioxide and krypton at 25oC. The mole fraction of the carbon
dioxide is 0.600 and there are 254 g of krypton. Calculate the total kinetic energy of the mixture.
16A. An unknown gas effuses at a rate of 31.2 mL/min. Under the same conditions, methane effuses at
45.6 mL/min. What is the molar mass of the unknown gas?
16B. It took 3.7 minutes for 2.7 L of helium to effuse through an opening in a container. How long will it take the
same volume of chlorine to effuse under identical conditions?
ANSWERS:
14A. 7.43 x 10–21 J
14B. 4.10 x 10–21 J
15. 28.2 kJ
16A. 34.2 g
16B. 16 min