Name ____KEY_________ Per. _________
SG 06 Gas Laws
Gases have several measurable properties. Temperature is a measure of the _average kinetic energy of_
(frequency of collisions by/ space occupied by/ maximum kinetic energy of/ average kinetic energy of) a substance’s
atoms or molecules. Temperature can be measured in degrees Fahrenheit or degrees Celsius, but during gas law
calculations we always use temperature measured in ____Kelvin____ (kilopascals/ Kelvin/ psi/ liters). To convert
from degrees Celsius to Kelvin you need to ______add 273______ (add 273/ subtract 273/ add 101.3/ multiply by
8.314).
Pressure is a measure of the ___frequency of collisions by___ (frequency of collisions by/ space occupied by/
maximum kinetic energy of/ average kinetic energy of) a substance’s atoms or molecules on a wall or surface. Another
way of describing pressure is force divided by surface area. We often use ____kilopascals___ (grams/ kilopascals/
Kelvin/ liters) as our units of measuring pressure, but [circle 3] (atm/ gallons/ mol/ psi/ mmHg/ ft3/ grams) are also
sometimes used.
Volume is a measure of the _____space occupied by_____ (frequency of collisions by/ space occupied by/
maximum kinetic energy of/ average kinetic energy of) a substance’s atoms or molecules. We often use
______liters_____ (grams/ kilopascals/ Kelvin/ liters) as our units of measuring volume, especially for gases.
Although we use graduated cylinders to measure the volume of liquids, we often need to use geometry to calculate the
inner volume of a container of gas because gases _spread out to fill their entire container_ (spread out to fill their
entire container/ only fill the bottom portion of their container/ do not spread out and remain in the same shape as they
started in).
There are several gas laws that allow us to use algebra to predict the properties of gases. The formula for
Boyle’s Law is P1 × V1 = P2 × V2 , which can be stated (as pressure increases volume decreases and vice versa/ as
V1
V2
pressure increases volume increases) when temperature is constant. The formula for Charles’ Law is
,
=
T1
T2
which can be stated (as temperature increases volume decreases / as temperature increases volume increases) when
P1
P2
pressure is constant. The formula for Gay-Lussac’s Law is
, which can be stated (as temperature
=
T1
T2
increases pressure decreases / as temperature increases pressure increases) when volume is constant.
The Combined Gas Law combines the formula from Boyles’, Charles’, and Gay-Lussac’s Laws to get the
P V
PV
formula 1 1 = 2 2 . Avogadro’s law is review from when we did mole conversions. It states that at STP 1
T1
T
mole of gas occupies a2volume of ___22.4 L___ (8.314 L/ 22.4 L/ 44.8 L/ 273 L). STP occurs at ______0˚C______
(0˚C/ room temperature/ 100˚C) and 1 atmosphere or 101.3 kPa of pressure. While the Combined Gas Law and most
of the other gas laws have a before and after, as shown by the small numbers 1 and 2, the Ideal Gas Law is only
concerned with the properties of a gas at a single moment in time. The Ideal Gas Law is P V = n R T , where n is the
kPa·L
number of moles and R is the gas constant. The gas constant, R, is 8.314 mol·K . This number will not change as long
as you are using kilopascals for pressure units and liters for volume units. The Ideal Gas Law begins to become
inaccurate at __very low__ (very high/ very low) temperatures, at __very high__ (very high/ very low) pressures, and
near the boiling point, which is also the condensation point, of gases.
The process of molecules, atoms, or ions spreading out from a high concentration to a low concentration in a
liquid or gas is called ___diffusion___ (graduation/ emulsion/ diffusion). It will take longer for perfume molecules to
spread out in a room full of air than in a room that has no air in it (a vacuum) because _______________________ (the
vacuum cleaner sucks/ the air molecules provide resistance to the diffusion/ perfume molecules are magnetically
attracted to air molecules).
An example of system at dynamic equilibrium is a liquid and a vapor together in a sealed container. The
amounts of liquid and vapor _may not be_ (may not be/ are always) equal, but they do remain constant. The rates of
liquid becoming a vapor and vapor becoming a liquid __are always__ (may not be/ are always) equal.
Match each gas property with its variable and unit.
Quantity
Temperature
Variable
n
Units
L
Moles
V
K
Pressure
T
mol
Volume
P
kPa
K = ˚C + 273
P1
P
= 2
T1
T2
P1 × V1 = P2 × V2
V1
V
= 2
T1
T2
V = (22.4 L/mol) × n
P1 × V1
P × V2
= 2
T1
T2
at STP (1 atm, 0˚C)
P×V=n×R×T
R = 8.314
kPa·L
mol·K
1) A balloon under pressure of 100 kPa is submerged below water until the pressure is 600 kPa. The original volume of
the balloon was 1.5 L. If the temperature did not change, what will the new volume be?
P1 × V1 = P2 × V2
(100)(1.5) = (600)V2
150 = (600)V2
600
600
V2 = 0.25 L
2) A piston filled with a gas at 0 ˚C has a volume of 1.2 L. If the piston and the gas inside it are heated, the volume
increases to 1.8 L. The pressure remains constant throughout this process. What was the temperature that the piston
was heated to?
V1
V2
=
T1
T2
1.2
1.8
=
273
T2
1.2 T2 = 491.4
1.2
1.2
T2 = 410 K
3) A balloon is measured to have a volume of 6.0 L at STP. How many moles of gas are held inside the balloon?
V = (22.4) × n
6.0 = (22.4)n
22.4 22.4
n = 3.6 mol
4) A propane tank with a fixed volume holds some propane gas at a pressure of 480 kPa when at 17 ˚C (290 K). As the
day warms up the temperature of the propane tank reaches 67 ˚C (340 K). What is the new pressure of the gas inside
the propane tank?
P1
P2
=
T1
T2
480
P2
=
290
340
163,200 = 290·P2
290
290
P2 = 563 kPa
5) The pressure of a gas decreases from 800 mm Hg to 600 mm Hg. Its temperature decreases from 100 ˚C to 60 ˚C.
What was the final volume of the gas if its initial volume is 2.4 L?
P1 × V1
P2 × V2
=
T1
T2
(800)(2.4) (600)V2
=
373
333
5.15 = 1.8·V2
1.8
1.8
V2 = 2.86 L
6) If a piston with a volume of 2.4 L contains 0.2 moles of gas under 300 kPa of pressure, what will the temperature of
the gas be in Kelvin? Assume it behaves as an ideal gas.
P×V=n×R×T
(300)(2.4) = (0.2)(8.314)T
720 = 1.663·T
1.663 1.663
T = 433 K