the gas laws
DESCRIPTION
The Gas Laws. Pressure. Force per unit area. Gas molecules fill container. Molecules move around and hit sides. Collisions are the force. Container has the area. Measured with a barometer. Vacuum. Barometer. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/1.jpg)
The Gas Laws
![Page 2: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/2.jpg)
04/21/23
Pressure
• Force per unit area.
• Gas molecules fill container.
• Molecules move around and hit sides.
• Collisions are the force.
• Container has the area.
• Measured with a barometer.
![Page 3: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/3.jpg)
04/21/23
Barometer• The pressure of the atmosphere at sea level will hold a column of mercury 760 mm Hg.
• 1 atm = 760 mm Hg
1 atm Pressure
760 mm Hg
Vacuum
![Page 4: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/4.jpg)
04/21/23
Units of pressure• 1 atmosphere = 760 mm Hg
• 1 mm Hg = 1 torr
• 1 atm = 101,235 Pascals
= 101.325 kPa
• Can make conversion factors from these.
![Page 5: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/5.jpg)
What is 724 mm Hg in torr?
1. 724 torr
2. 96.5 torr
3. 0.953 torr
4. 73,359 torr
![Page 6: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/6.jpg)
What is 724 mm Hg in kPa?
1. 724 kPa
2. 96.5 kPa
3. 0.953 kPa
4. 73,359 kPa
![Page 7: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/7.jpg)
What is 724 mm Hg in atm?
1. 724 atm
2. 96.5 atm
3. 0.953 atm
4. 73,359 atm
![Page 8: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/8.jpg)
04/21/23
The Gas Laws• Boyle’s Law• Pressure and volume are inversely
related at constant temperature.• PV= k• As one goes up, the other goes
down.
• P1V1 = P2 V2
• Graphically
![Page 9: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/9.jpg)
04/21/23
V
P (at constant T)
![Page 10: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/10.jpg)
04/21/23
V
1/P (at constant T)
Slope = k
![Page 11: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/11.jpg)
04/21/23
Examples
• 20.5 L of nitrogen at 25ºC and 742 torr are compressed to 9.8 atm at constant T. What is the new volume?
1. 2.04 L
2. .264 L
3. .467 L
![Page 12: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/12.jpg)
30.6 mL of carbon dioxide at 740 torr is expanded at constant temperature to 750 mL. What is the final pressure in kPa?1. 30.2 kPa
2. .0397 kPa
3. 4.025 kPa
4. 169843 kPa
![Page 13: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/13.jpg)
Charles' Law
• Volume of a gas varies directly with the absolute temperature at constant pressure.
• V = kT (if T is in Kelvin)
• V1 = V2
T1 = T2
• Graphically
![Page 14: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/14.jpg)
04/21/23
V (
L)
T (ºC)
He
H2O
CH4
H2
-273.15ºC
![Page 15: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/15.jpg)
04/21/23
Examples
• What would the final volume be if 247 mL of gas at 22ºC is heated to 98ºC , if the pressure is held constant?
1. 1100 mL
2. 196 mL
3. 311 mL
![Page 16: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/16.jpg)
• At what temperature would 40.5 L of gas at 23.4ºC have a volume of 81.0 L at constant pressure?
1. 592.8 K
2. 592.8 0C
3. 319.8 K
![Page 17: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/17.jpg)
04/21/23
Avogadro's Law• At constant temperature and
pressure, the volume of gas is directly related to the number of moles.
• V = k n (n is the number of moles)
• V1 = V2 n1
= n2
![Page 18: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/18.jpg)
04/21/23
Gay- Lussac Law
• At constant volume, pressure and absolute temperature are directly related.
• P = k T
• P1 = P2 T1
= T2
![Page 19: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/19.jpg)
04/21/23
Combined Gas Law• If the moles of gas remains constant,
use this formula and cancel out the
other things that don’t change.
• P1 V1 = P2 V2
. T1 T2
![Page 20: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/20.jpg)
04/21/23
Ideal Gas Law
• PV = nRT• V = 22.41 L at 1 atm, 0ºC, n = 1
mole, what is R?• R is the ideal gas constant.• R = 0.08306 L atm/ mol K• Tells you about a gas is NOW.• The other laws tell you about a gas
when it changes.
![Page 21: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/21.jpg)
04/21/23
Ideal Gas Law• A hypothetical substance - the ideal
gas• Think of it as a limit.• Gases only approach ideal behavior
at low pressure (< 1 atm) and high temperature.
• Use the laws anyway, unless told to do otherwise.
• They give good estimates.
![Page 22: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/22.jpg)
Example
• A 47.3 L container containing 1.62 mol of He is heated until the pressure reaches 1.85 atm. What is the temperature?
1. 316 K
2. 658 K
3. 27.1 K
![Page 23: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/23.jpg)
04/21/23
Gas Density and Molar Mass
• D = mass/Volume
• Let MMstand for molar mass
• MM = mass/n
• n= PV/RT
• PV = mass RT
MM
![Page 24: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/24.jpg)
Example
• What is the density of ammonia at 23ºC and 735 torr?
1. 0.676 g/L
2. 0.987 g/L
3. 1.20 g/L
![Page 25: The Gas Laws](https://reader035.vdocument.in/reader035/viewer/2022062315/5681554b550346895dc31acf/html5/thumbnails/25.jpg)
04/21/23
Gases and Stoichiometry
• Reactions happen in moles
• At Standard Temperature and Pressure (STP, 0ºC and 1 atm) 1 mole of gas occupies 22.42 L.
• If not at STP, use the ideal gas law to calculate moles of reactant or volume of product.