Unit 4
Name _______________________________
# ________
Section 1: Gas Properties
1. How are gases different than solids and liquids?
Section 2: Graham’s Law
1. Helium effuses through a porous cylinder 3.20 times faster than a certain
compound. What is the compound’s molar mass?
2. What is the formula weight of a gaseous element if at room temperature it
effuses though a pinhole 2.165 times as rapidly as xenon? Which element is it?
3. An unknown gas effuses through a capillary in 60 seconds. The same volume of
hydrogen escapes in 10 seconds. Calculate the molecular mass of the unknown
gas.
4. A bicycle pump is filled with helium (He) gas. With constant pressure, the gas is
forced out through a small aperture in five seconds. How long will it take to expel
sulfur dioxide, SO2, from this same pump under the same constant pressure?
Section 3: Pressure conversions
1. Convert 755 Torr to atmospheres.
2. Convert 15.3 psi to atmospheres.
3. Convert 24.3 mm Hg to Torr.
4. Convert 463.1 mmHg to bars.
5. Convert 35psi to in Hg.
6. Convert 14.7 psi to bar.
7. Convert 14.7 bar to kPa
8. Convert 0.03 kPa to Pa.
Section 4: Pressure in Manometers
1. According to the diagram of closed-ended manometers below:
a. What must be true about A? __________________
b. Which of the manometers contains the gas with the highest pressure? ___
c. If A was open-ended instead, what would be true about it?
________________________________________________
2. Calculate the pressure of a gas in kPa if a sample in a closed end manometer
has a change in Hg height of 76.9 mm Hg.
3. In an open end manometer the Hg level is 22.5 mm Hg higher in the arm
attached to the gas sample. Calculate the gas pressure in atm if the atmospheric
pressure is 1146.5 mb.
4. Calculate the gas pressure (in mm Hg) in an open end manometer where the Hg
level is 35mm higher in the atmospheric arm if the atmospheric pressure is
30.25 in Hg.
Section 5: Partial Pressures
1. The gas from an erupting volcano had the following composition: 65.0% CO 2,
25.0% H2, 5.4% HCl, 2.8% HF, 1.7% SO2, and 0.1% H2S. What are the partial
pressures of each gas if the total pressure is 760.0 mm of Hg?
2. A container of gases consists of the following mixture of gases: 2.0 moles of
helium, 6.0 moles of carbon dioxide, 10.0 moles of neon, and 12.0 moles of
xenon. If the total pressure is 900.0 mm of Hg, determine the partial pressure of
each gas.
3. Nitrogen is collected over water at 21.5C (vapor pressure is 18.7 mm Hg). What
is the partial pressure of nitrogen if the atmospheric pressure is 99.4 kPa?
4. Argon is collected over water at 30C (vapor pressure is 31.8 mm Hg). Find the
pressure of the dry gas if the barometric pressure is 0.975 atm.
Section 6: Ideal Gas Law
1. Complete the following statements by determining whether a decrease or
increase will occur:
a. The volume of a gas will ___________________________ if its
temperature is increased.
b. The temperature of a gas will ________________________ if its volume
is decreased.
c. The pressure of a gas will _________________________ if its volume is
decreased.
d. The volume of a gas will __________________________ if its pressure is
increased.
2. If I have 4 moles of a gas at a pressure of 5.6 atm and a volume of 12 liters, what
is the temperature?
3. If I have an unknown quantity of gas at a pressure of 1.2 atm, a volume of
31 liters, and a temperature of 87 °C, how many moles of gas do I have?
4. If I contain 3 moles of gas in a container with a volume of 60 liters and at a
temperature of 400 K, what is the pressure inside the container?
5. If I have 7.7 moles of gas at a pressure of 0.09 atm and at a temperature of
56 °C, what is the volume of the container that the gas is in?
6. If I have 17 moles of gas at a temperature of 67 °C, and a volume of 88.89 liters,
what is the pressure of the gas?
7. If I have an unknown quantity of gas at a pressure of 0.5 atm, a volume of
25 liters, and a temperature of 300 K, how many moles of gas do I have?
8. If I have 21 moles of gas held at a pressure of 78 atm and a temperature of
900 K, what is the volume of the gas?
9. If I have 1.9 moles of gas held at a pressure of 5 atm and in a container with a
volume of 50 liters, what is the temperature of the gas?
10. If I have 2.4 moles of gas held at a temperature of 97 °C and in a container with a
volume of 45 liters, what is the pressure of the gas?
11. If I have an unknown quantity of gas held at a temperature of 1195 K in a
container with a volume of 25 liters and a pressure of 560 atm, how many moles
of gas do I have?
12. If I have 0.275 moles of gas at a temperature of 75 K and a pressure of
1.75 atmospheres, what is the volume of the gas?
13. If I have 72 liters of gas held at a pressure of 3.4 atm and a temperature of
225 K, how many moles of gas do I have?
Section 7: Avogadro’s Law
1. What is the volume in mL of 88.3 mg of carbon dioxide gas at STP?
2. How many grams of gas must be released from a 45.2 L sample of N2 at STP to
reduce the volume to 45.0 L at STP?
Section 8: Gas Density Problems
1. Calculate the density of HCl at STP.
2. Calculate the density of H2S at STP.
3. The density of hydrogen is 9.00 x 10-2 g/L. What will be the mass of 100 liters?
4. The density of an elemental gas is 1.25 g/L at STP. What is the mass of 1 mole?
What could this gas be?
Section 9: Gas Stoichiometry
1. What volume of nitrogen gas is needed to react completely with magnesium to
form 75 grams of magnesium nitride at a pressure of 1.25 atm and a temperature
of 20°C.
2. If 4.0 liters of nitrogen reacts with 10.0 liters of hydrogen at STP – what is the
mass (in grams) of Ammonia, NH3, produced?
3. PCl5 when heated decomposes into chlorine gas and phosphorus trichloride. If 45
liters of chlorine gas is produced at STP what is the mass of PCl5 required to do
this reaction?
4. What volume of water vapor would be produced from the complete reaction of 25
grams of hydrogen with excess oxygen at STP?
Section 10: Gas Stoichiometry
The following problems deal with reactions that occur at STP:
1. Carbon monoxide reacts with oxygen to produce carbon dioxide. If 1.0 L of
carbon monoxide reacts with oxygen at STP,
a. how many liters of oxygen are required to react?
b. how many liters of carbon dioxide are produced?
2. Acetylene gas (C2H2) undergoes combustion by reacting with oxygen to produce
carbon dioxide and water vapor.
a. How many liters of C2H2 are required to produce 75.0 L of CO2?
b. What volume of H2O is produced?
c. What volume of O2 is required?
3. If liquid carbon disulfide (CS2) reacts with 450 mL of oxygen to produce the
gases carbon dioxide and sulfur dioxide at STP, what volume of each product is
produced?
4. Assume that 5.60 L of hydrogen gas at STP reacts with copper (II) oxide
according to the following balanced equation:
CuO (s) + H2 (g) 
2O (g)
a. How many moles of H2 react?
b. How many moles of copper are produced?
c. How many grams of copper are produced?
5. Assume that 8.5 L of iodine gas (I2) are produced at STP according to the
following balanced equation:
2 KI (aq) + Cl2 (g) 
2 (g)
a. How many moles of I2 are produced?
b. How many moles of KI were used?
c. How many grams of KI were used?
6. Solid iron(III) hydroxide decomposes to produce iron(III) oxide and water vapor. If
0.75 L of water vapor are produced at STP,
a. how many grams of iron(III) hydroxide were used?
b. how many grams of iron(III) oxide were produced?
7. Solid iron reacts with sulfuric acid to produce iron(II) sulfate and hydrogen gas. If
650 mL of hydrogen gas are collected at STP, how many grams of iron(II) sulfate
are also produced?
8. Assume that 13.5 grams of solid aluminum react with HCl according to the
following balanced equation at STP:
2 Al (s) + 6 HCl (aq) 
3 (aq) + 3 H2 (g)
a. How many moles of Al react?
b. How many moles of H2 are produced?
c. How many liters of H2 are produced?
The following problems deal with reactions that do not occur at STP:
9. Ammonium sulfate, an important fertilizer, can be prepared by the reaction of
ammonia with sulfuric acid according to the following balanced equation:
2 NH3 (g) + H2SO4  (NH4)2SO4 (aq)
Calculate the volume of NH3 (in liters) needed at 20ºC and 25.0 atm to react with
150 kg of H2SO4.
10. If 45.0 L of natural gas, which is essentially methane (CH4), undergoes complete
combustion at 730 mm Hg and 20ºC, how many grams of each product are
formed?
11. Fritz Haber, a German chemist, discovered a way to synthesize ammonia gas
(NH3) by combining hydrogen and nitrogen gases at extremely high temperatures
and pressures.
a. Write the balanced equation for this reaction.
b. If 10 kg of nitrogen combines with excess hydrogen at 550ºC and 250 atm,
what volume of ammonia gas is produced?
12. A 3.25 gram sample of solid calcium carbide (CaC2) reacts with water to produce
acetylene gas (C2H2) and aqueous calcium hydroxide. If the acetylene was
collected over water at 17ºC and 740.0 mm Hg, how many milliliters of acetylene
were produced?
Section 11: Combined Gas Law
1. A child receives a balloon filled with 2.30 L of helium from a vendor at an
amusement park. The temperature outside is 311 K. What will be the volume of
the balloon when the child brings it home to an air-conditioned house at 295 K?
2. 1.00 L of a gas at standard temperature and pressure is compressed to 473 mL.
What is the new pressure of the gas?
3. A gas takes up a volume of 17 liters, has a pressure of 2.3 atm, and a
temperature of 299 K. If I raise the temperature to 350 K and lower the pressure
to 1.5 atm, what is the new volume of the gas?
4. A small 2.00 L fire extinguisher has an internal pressure of 506.6 kPa at 25 oC.
What volume of methyl bromide, the fire extinguisher’s main ingredient, is
needed to fill an empty fire extinguisher at standard pressure if the temperature
remains constant?
5. I have an unknown volume of gas at a pressure of 0.5 atm and a temperature of
325 K. If I raise the pressure to 1.2 atm, decrease the temperature to 320 K, and
measure the final volume to be 48 liters, what was the initial volume of the gas?
6. On hot days, you may have noticed that potato chip bags seem to “inflate”, even
though they have not been opened. If I have a 250 mL bag at a temperature of
19 °C, and I leave it in my car that has a temperature of 60 °C, what will the new
volume of the bag be?
7. A helium balloon has a volume of 500. mL at STP. What will be its new volume if
the temperature is increased to 325 K and its P is increased to 125 kPa?
8. A cylinder of argon gas contains 125 mol at a pressure of 150 atm and a
temperature of 27°C. After some of the argon has been used, the pressure is
136 atm at 27°C. What mass of argon remains in the cylinder?
9. A soda bottle is flexible enough that the volume of the bottle can change even
without opening it. If you have an empty soda bottle (volume of 2 L) at room
temperature (25 °C), what will the new volume be if you put it in your freezer
(-4 °C)?
10. Some students believe that teachers are full of hot air. If I inhale 2.2 liters of gas
at a temperature of 18 °C and it heats to a temperature of 38 °C in my lungs,
what is the new volume of the gas?
11. Synthetic diamonds can be manufactured at pressures of 6.00 x 104 atm. If
2.00 liters of gas at 1.00 atm is compressed to a pressure of 6.00 x 104 atm, what
would the volume of that gas be?
12. If a gas has a volume of 3.00 L, a pressure of 740. Torr and a temperature of
310. K what will be its new temperature in oC if the pressure is increased to
1.50 atm while keeping the volume constant?
13. If I initially have a gas at a pressure of 12 atm, a volume of 23 liters, and a
temperature of 200 K, and then I raise the pressure to 14 atm and increase the
temperature to 300 K, what is the new volume of the gas?
14. Atmospheric pressure on the peak of Mt. Everest can be as low as 150 mm Hg,
which is why climbers need to bring oxygen tanks for the last part of the climb. If
climbers carry 10.0 liter tanks with an internal gas pressure of 3.04 x 10 4 mm Hg,
what will be the volume of the gas when it is released from the tanks?
15. A man heats a balloon in the oven. If the balloon’s initial volume is 0.4 liters and
has a temperature of 20 °C, what will the volume of the balloon be after he heats
it to a temperature of 250 °C?
Section 12: Combined Gas Law
1. If 400 cm3 of oxygen is collected at a pressure of 980 mmHg, what volume will
the gas occupy if the pressure were changed to 940 mmHg?
2. What is the volume of hydrogen at a pressure of 1.06 atm if 200 cm3 of hydrogen
is collected at a pressure of 1.00 atm?
3. The pressure on 2.50 L on anesthetic gas changes from 760 mmHg to
304 mmHg. What will be the new volume if the temperature remains constant?
4. How hot will a 2.3 L balloon have to get to expand to a volume of 400 L?
Assume that the initial temperature of the balloon is 25 °C.
5. A gas sample occupies 200 mL at 760 mmHg. What volume does the gas
occupy at 400 mmHg?
6. Nitrogen gas in a steel cylinder is under pressure of 150 atm at 27°C. What will
the pressure in the tank be if the tank is left in the sun and the internal
temperature rises to 55°C?
7. If a sample of a gas occupies 6.8 L at 327°C, what will be its volume at 27°C if
the pressure does not change?
8. A gas occupies a volume of 560 cm3 at a temperature of 100°C. To what
temperature must the gas be lowered to if it is to occupy 400 cm 3? Assume
constant pressure.
9. What temperature would a gas sample have if it started at 25°C and it went from
a pressure of 0.59 atm to 799 Torr, while the volume changed from 3.43 L to
99.8 mL, and the number of moles went from 3.1 to 12.2?
10. If a balloon contains 0.75 mol of O2 at 28°C and has a volume of 2.8 L, what will
be the volume, in L, if an additional 16 g of O2 is added at the same temperature
and pressure?
11. A gas has a temperature of 14 °C, and a volume of 4.5 liters. If the temperature
is raised to 29 °C and the pressure is not changed, what is the new volume of the
gas?
12. If I have 17 liters of gas at a temperature of 67 °C and a pressure of 88.89 atm,
what will be the pressure of the gas if I raise the temperature to 94 °C and
decrease the volume to 12 liters?
13. If I have 21 liters of gas held at a pressure of 78 atm and a temperature of 900 K,
what will be the volume of the gas if I decrease the pressure to 45 atm and
decrease the temperature to 750 K?
14. I have an unknown volume of gas held at a temperature of 115 K in a container
with a pressure of 60 atm. If by increasing the temperature to 225 K and
decreasing the pressure to 30 atm causes the volume of the gas to be 29 liters,
how many liters of gas did I start with?
15. Divers get “the bends” if they come up too fast because gas in their blood
expands, forming bubbles in their blood. If a diver has 0.05 L of gas in his blood
under a pressure of 250 atm, then rises instantaneously to a depth where his
blood has a pressure of 50.0 atm, what will the volume of gas in his blood be?