# Chem Unit 12 HW Packet ```How do Gases Behave?
Chemistry Unit 12: HW Packet
Name:_____________________________
____ / 145 pts
Main Idea:

Gases respond in predictable ways to pressure, temperature, volume and changes in
number of particles.
New Skills:
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Convert pressure units
Solve problems using the individual gas laws and the combined gas law.
Solve problems using the ideal gas law
Solve gas stoichiometric problems
PV = nRT
PV PV
=
T
T
R = 0.08206
12.1 The Gas Laws - For a fixed amount of gas, a change in one variable- pressure,
temperature, or volume – affects the other two.
1. State the relationship among pressure, temperature and volume of a constant amount of
gas.
a. (8pts) What are the equivalent units for 1atm? Please include torr, mmHg, Pa and
kPa.
1atm =
b. (2pts) How are pressure and volume related, direct or indirect?
c. (2pts) How are temperature and volume related, direct or indirect?
d. (2pts) How are temperature and pressure related, direct or indirect?
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2. Apply the gas laws to problems involving the pressure, temperature, and volume of a
constant amount of gas.
a. (5pts) A sample of helium gas has a volume of 1.24 L at 0.865 atm. The temperature
is kept constant but the pressure is increased to 2.56 atm. What is the volume of the
helium gas at the new pressure?
b. (5pts) A child’s balloon that has 1.5L of helium is left in a car on a summer day. The
car is initially at 32&deg;C but quickly increases to 82&deg;C. What is the new volume of the
balloon assuming that the pressure stays constant?
c. (5pts) What is the pressure of a fixed volume of hydrogen gas at 30.0&deg;C if it has a
pressure of 1.25 atm at 15.0&deg;C?
d. (5pts) A weather balloon is filled with helium that occupies a volume of 5.00x103 L at
0.996 atm and 32.2&deg;C. After it is released, it rises to a location where the pressure is
0.645 atm and the temperature is -18.8&deg;C. What is the new volume of the balloon?
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13.2 The Ideal Gas Law - The ideal gas law relates the number of particles to pressure,
temperature, and volume.
1. Relate number of particles and volume using Avogadro’s principle.
a. (2pts) How much volume does 1 mole of gas occupy at standard conditions?
b. (6pts) What does STP stand for and what specific numbers does it represent?
c. (5pts) How many moles does a sample of gas have if it has a volume of 96.8 L at
STP?
d. (8pts) Propane (C3H8) is often used for grilling. How much volume would 20.0 lbs of
propane occupy if the gas were at STP? (Most ‘20lb’ propane steel containers weigh
~18lbs empty, but hold approximately 20lbs of propane. 1pound = 453.6 grams)
2. Relate the amount of gas present to its pressure, temperature, and volume using the ideal
gas law.
a. (4pts) What units must be used in the ideal gas law equation?
b. (8pts) What is the pressure of the propane inside of a full 20.lb propane container if
it has a volume capacity of 21 Liters?
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c. (8pts) What is the density (in grams/ml) of a sample of nitrogen gas (N2) that exerts
a pressure of 5.30 atm in a 3.65 L container at 135&deg;C?
1. Compare the properties of real and ideal gases.
a. (6pts) What are the three ideal assumptions of kinetic molecular theory?
i.
ii.
iii.
b.
(4pts) What conditions make gases behave as ideal gases?
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13.3 Gas Stoichiometry- When gases react, the coefficients in the balanced chemical
equation represent both molar amounts and relative volumes.
1. Determine volume ratios for gaseous reactants and products by using coefficients
from chemical equations.
a. (5pts) What volume of oxygen gas is needed for the complete combustion of 20.0lbs
of propane gas (C3H8)? Assume that pressure and temperature remain constant.
(hint: you will need a balanced equation).
b. (10pts) Ammonia is synthesized from hydrogen and nitrogen.
N2(g) + 3H2(g)  2NH3(g)
If 8.00 L of nitrogen reacts completely with hydrogen at a pressure of 2.20 atm and a
temperature of 312 K, how much ammonia, in grams, is produced?
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c. (10pts) What volume of H2O(g) measured at STP is produced by the combustion of
10.843 g of natural gas (CH4) according to the following equation?
CH4 (g) + 2O2 (g)  CO2 (g) + 2H2O(g)
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2. Apply gas laws to calculate amounts of gaseous reactants and products in a chemical
reaction.
a. (10pts) Calcium hydride combines with water according to the equation
CaH2 (s) + 2H2O(l)  2H2 (g) + Ca(OH)2 (s)
Beginning with 124.0 g of CaH2 and 86.0 g of H2O, what volume of H2 will be
produced at 273 K and a pressure of 1609 torr?
b. (10pts) A baker uses baking soda as the leavening agent for pecan pie. The baking
soda (sodium hydrogen carbonate) decomposes into sodium carbonate, water and
carbon dioxide. Calculate the volume of carbon dioxide that forms for every gram of
baking soda used. Assume the reaction takes place at 320&deg;C and 1.00 atm.
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c. (15pts) Acetylene is often used for welding and burns according to the following
equation:
2C2H2(g) + 5O2(g)  2H2O(g) + 4CO2(g)
If you have an 280 liter tank of acetylene at 1700. kPa and a 280 liter tank of oxygen
at 1250 kPa, how many grams of water vapor and carbon dioxide are produced if the
temperature of tanks and the products are at 32.0&deg;C?
12.4 Accumulating Content and Skills– Chemistry content is continuous and builds on
prior knowledge and skills. This section will combine this unit with previous units.
1. Apply knowledge and skills from previous units to content learned in this unit.
 Write a one-page paper (single spaced) about how chemistry and gases are related.
This paper is should be emailed or printed and handed in separately.
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