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More About GasesCharles’ LawGay-Lussac’s LawKinetic Molecular Theory (KMT)
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Charles’ LawJacques Charles determined the relationship between temperature and volume of a gas.He measured the volume of air at different temperatures, and observed a behavior pattern which led to his law.During his experiments pressure of the system and amount of gas were held constant.
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Temperature
The temperature of a gas is generally measured with a thermometer in Celsius. All calculations involving gases should be made after converting the Celsius to Kelvin temperature.
Kelvin = C° + 273
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Volume of balloon at
room temperature
Volume of balloon at
room temperature
Volume of balloon at 5°C
Volume of balloon at 5°C
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Charles’ Law
Example: A gas has a volume of 3.0 L at 127°C. What is its volume at 227 °C? V1 V2
T1 T2
=
T1 = 127°C + 273 = 400K
V1 = 3.0 L
T2 = 227°C + 273 = 500K
V2 = ?
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2) Plug in the variables:
2) Plug in the variables:
(500K)(3.0L) = V2 (400K)(500K)(3.0L) = V2 (400K)
V2 = 3.75 LV2 = 3.75 L
3.0L V23.0L V2
400K 500K400K 500K
=
=3) Cross multiply and
solve3) Cross multiply and
solve
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Gay-Lussac’s Law: P and T
In Gay-Lussac’s Law
the pressure exerted by a gas is directly related to the Kelvin temperature.
Volume and the amount of gas are constant.
P1 = P2
T1 T2
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Calculation with Gay-Lussac’s Law
A gas has a pressure at 2.0 atm at 18°C. What is the new pressure when the temperature is 62°C? (Volume and the amount of gas are constant)
1. Set up the problem:
P1 = 2.0 atm P2 =
T1 = 18°C + 273 T2 = 62°C + 273 = 291 K = 335 K
?
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Calculation with Gay-Lussac’s Law (continued)
2. Solve Gay-Lussac’s Law for P2:
P1 = P2
T1 T2
P2 = P1 x T2
T1
P2 = 2.0 atm x 335 K = 2.30 atm 291 K
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What is Kinetic Molecular Theory (KMT)?
• A theory that envisions molecules in motion
• Best describes properties and behaviors of gases
* Imagines particles of a gas like ping pong balls, moving and crashing into each other and the walls of a container in a three-dimensional space.
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Basic Principles of KMT
1. Gases consist of tiny particles.
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2. Gas particles are very far apart; the volume occupied by a gas consists mostly of empty space (typically about 99.9% empty).
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3. Gas particles move randomly in all directions, traveling in straight lines.
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Gas particles collide with each other and with the walls of the container without losing energy.
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4. The higher the average speed of the particles, the higher the temperature of that substance.