Gases Notes
Name______________________________________
Period________Date__________________________
12.1 A. Physical Properties:
1. Gases have _____________. The density is much smaller than ________________ or
________________, but they have mass.
2. Gases can be _________________________. Very easy to reduce the _____________
of a gas. Example: __________________________________________________________
3. Gases completely _____________ their containers.
4. Gases can _______________ through each other rapidly. Example the
_________________________ of food smells and perfume.
5. Gases exert ______________________.
6. The _____________________ of a gas depends upon _________________________.
High Temp. = _____________ pressure,
low temp. = ______________ pressure.
B. Kinectic - Molecular Theory:
1. Gases are _______________ particles that have _____________. These particles are
usually molecules, except for the ______________________________.
2. The particles in gases are separated by relatively __________________ distances.
3. The particles in gases are in constant rapid _________________ (random).
4. Gases exert pressure because their particles frequently ______________________
with the walls of their ________________________ and each other.
5. Collisions of gas particles are perfectly _______________________.
6. Temperature of a gas is simply a measure of the _____________________ energy of
the gas particles. High temp. = ___________ K.E., Low temp. = ___________ K. E.
7. Gas particles exert no _________________ on one another. Attractive forces are so
________________ between particles they are assumed to be _______________.
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C. Measuring Gases:
1. The following 4 variables will be used to do gas calculations:
______ - amount of a gas, it is measured in _____________
______ - volume of a gas, it is measured in ______________________________
“STP” = Standard Temperature & Pressure:
______- Standard Temperature:
_________ oC = _________K
Taken in oC converted to Kelvin (K)
Ex #1) 22°C = ________ K
-27.3°C
= ________ K
T(K) =
100.°C = ________ K
-273°C
= _______ K
______- Standard Pressure: can be measured using the following units:
(sea level pressure)
________________ atm (atmospheres)
__________mm Hg
________________ Pa (Pascals)
__________torr
________________ kPa (kilopascals)
__________lb/in2 (psi)
Ex #2) Convert 1.026 atm to kPa:
Ex #3) Convert 98,500 Pa to mm Hg:
2. Atmospheric pressure is the pressure exerted by the ________________ in the atmosphere.
This pressure varies with altitude and ______________ ______________ ________________
3. Atmospheric pressure is measured with a _______________________. This is a glass tube
sealed at one end and filled with Hg.
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12.2 The Gas Laws
A. Boyle’s Law: Pressure - Volume Relationship. The pressure & volume of a sample of
gas at constant ______________________ are ____________________ proportional to each
other.
Ex #4) A gas has a volume of 300. mL under a pressure of 740. mm of mercury. If the temperature
remains constant, calculate the volume when under a pressure of 750. mm.
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B. Charles’ Law: Temperature - Volume Relationship. At constant _________________
the volume of a fixed amount of gas is ___________________ proportional to its absolute
________________________.
* Temperatures must be in Kelvin!!
K = oC + _______
Ex #5) What is the Celsius temperature of 68.20 mL of methane, if it occupies a volume of
0.02200 L at 50.0 oC?
C. Avogadro’s Law: Amount - Volume Relationship. Equal ___________________ of gases at
the same _______________________ and _________________________ contain an
________________ number of particles.
1 mole gas = _____________ = 6.02 x 1023 particles at STP (273 K & 1 atm)
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He
O2
Rn
Therefore because of Avogadro’s Law if these three gases are at the same temperature and pressure,
they must take up the same ______________________.
D. Dalton’s Law of Partial Pressures: The sum of the partial ______________________
of all the components in a gas mixture is equal to the total ______________________
of the gas mixture.
Ex #6) A flask contains a mixture of oxygen, argon, and carbon dioxide with partial pressures
of 745 torr, 0.278 atm, and 391 torr respectively. What is the total pressure in the
flask?
Ex #7) 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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E. The Combined Gas Law: “Choyles” This law can be used to determine how changing two
variables at a time affects a _________________ variable.
Ex #8) A gas occupies 72.0 mL at 25 oC and 198 kPa. Convert these to standard conditions.
What is the new volume?
P1 =
V1 =
T1 =
P2 =
V2 =
T2=
12.3
A.The Ideal Gas Law
Although no “ideal gas” exists, this law can be used to explain the __________________
of _______________ gases under ordinary conditions.
P = __________________________
V = __________________________
n = __________________________
R = __________________________
universal gas constant
T = __________________________
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B. Ideal Gas Law & The Kinetic – Molecular Theory:
1. Under normal conditions (temperature & pressure) gases behave ____________________.
PV = nRT
n ____
P ____
(more gas, _________________________)
T ____
P ____
(moves faster, ______________________)
V ____
P ____
(smaller volume, ____________________)
2. Gases at ___________________________ and ____________________________ do NOT behave
ideally. As you decrease the volume of a gas, the __________________ of the particles themselves
__________________ ______________________. The Kinectic-Molecular Theory & Ideal Gas Law
assume that gas particles have _____ _______________ of their own.
3. Second, the __________________ ________________ which are very ____________ when
the particles are moving fast, become larger as they _____________ _____________.
Ex #9) How many grams of carbon dioxide occupy a volume of 36.9 mL at 158 kPa and 72 °C?
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C. Lifting Power of Gases:
1. Uses a gas “____________________________” than air (smaller ________________ mass.)
Ex) The Hindenburg used
______________________________________
Ex) Today’s blimps use
______________________________________
2. Hot Air balloons heat air to lower its ________________________.
3. Effusion is the movement of gas atoms or molecules through a hole so ______________ they
move one particle at a time. Smaller particles effuse ____________________ than larger particles.
Ex)
→
→
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