Name ____________________________________
Period ____________
Unit 8: Gas
8-1 Properties of Gas
1. What are the properties of gasses?
a. Gas – a state of matter that has no fixed shape or volume
i. Gasses are fluids
ii. Gases have mass and a volume and density (density is usually low)
iii. Compressible
iv. Will expand to completely fill their containers. (click)
v. Gases can move through each other rapidly.
vi. Exert a pressure (click)
1. The pressure of a gas exerts depends upon temperature of the gas
 High Temp. = high pressure = gas particles are moving quickly so
hitting walls of container harder
 Low temp. = low pressure = gas particles are moving slowly so
hitting walls of container softer (click)
2. How do we quantify Gases?
a. There are 4 variables used to do gas calculations:
i. N - amount of a gas molecules (moles)
ii. V- volume of a gas, (L)
iii. T- Temperature (K or oC)
1. C = K-273
2. K= C+273
iv. P- Pressure
1. 1atm (atmospheres)= 101325Pa (Pascals)= 760mm Hg or torr= 14.7 lb/in2 (psi)
b. “STP” = Standard Temperature & Pressure: 1 atmosphere of pressure and 0oC (273K)
8-2 The Gas Laws
1. What is the Combined Gas Law?
Combined Gas Law
(Choil’s Law):
𝑃1 𝑉1
𝑃2 𝑉2
=
𝑇1
𝑇2
The combined gass law is used to determine how changing a gasses pressure voliume, and or temperature will effect
the others
Gas law animations
can crush
Sample Combined Gas Law Problems:
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1. 72.0 mL of O2 at 25 oC is at a pressure of 198 KPa. Determine the volume that the gas will occupy at
STP.
2. A sealed 1000L hot air balloon takes off at ground level (1atm) on a sunny day (25 oC). What will the
volume of the balloon be at a altitude of 30,000 ft. where the pressure is 0.63atm and the
temperature is 15oC?
2. What is Dalton’s Law of Partial Pressures of gasses?
Dalton’s Law of Partial
Pressures of gasses:
PTOTAL = PA +PB + PC . . . .
a. In a mixture of gases, each individual gas exerts a portion of the total pressure of the mixture. The sum of
the partial pressures of all the components in a gas mixture is equal to the total pressure of the gas
mixture.
Sample Daltons Law Problems:
1. A flask contains a mixture of oxygen, argon, and carbon dioxide with partial pressures of 745 torr, 0.278
atm, and 391 mmHg respectively. What is the total pressure in the flask?
2. The total pressure of a mixture of helium and neon is 498 mm Hg. If helium is 20.0 % of the mixture, what
is the partial pressure of helium?
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3. What the air pressure in a greenhouse if a barometer reads 792mmHg the vapor pressure of water is
measured to be 30mmHg?
8-3 Avogadro’s Law
3. What is Avogadro’s law?
a. Avogadro’s law states that since there is such a large space between gas particles, the volume a gas
occupies is not dependant on the molar mass or size of the gas particle
b. As long as temperature and pressure are the same, 1 mole of any gas will occupy the same volume
c. At STP all gasses occupy 22.4L no matter what gas they are
Sample mole gas conversations:
4. How many L will 8 moles of CO2 occupy at STP?
5. How many moles of particles are in 44.8L?
8-4 The ideal gas Law
1. What is an ideal gas?
a. An ideal gas is a imaginary gas who’s particles don’t have any volume and don’t ever collide
b. Although no “ideal gas” exists, under ordinary pressures and temperatures gas behaves ideally and
thus can be treated as an ideal gas
2. What is the ideal gas law?
a. The ideal gas law was determined by measuring a series of gasses (1mol of them) at the same
pressure temperature and volume.
i. It was found that no matter what the gas was, when you divide the product of the pressure
and volume by the product of the number of moles of gas there where wand the
temperature you always get the same number, R (the universal gas constant
𝑎𝑡𝑚 ∙𝐿
R = 0.0821𝑚𝑜𝑙 ∙𝐾
or
𝑃𝑉
𝑁𝑇
= 0.0821
The Ideal Gas Law:
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𝑃𝑉 = 𝑛𝑅𝑇
ii. However, because the units for P,V, N, and T can change R is unit specific
iii. In order to use 0.0821 as R you must have the following units:
P = atm
V =L
n = number of moles
T = Kelven
Ideal Gas Law Problems:
1. How many grams of carbon dioxide occupy a volume of 36.9 mL at 158 KPa and 72 oC?
2. How much would a 20lb 8L SCUBA tank way at 22oC if it were filled with oxygen gas until the
pressure inside the tank was 200atm?
3. What volume of gas would be produced if a 1Kg chunk of dry ice (solid CO2) turned completely to
gas at sea level (1atm) and room temperature (22oC)
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