January 31, 2008 Go over homework Charles’s Law Avogadro’s Law Homework -- Page 480 -- 11, 13,...
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Transcript of January 31, 2008 Go over homework Charles’s Law Avogadro’s Law Homework -- Page 480 -- 11, 13,...
![Page 1: January 31, 2008 Go over homework Charles’s Law Avogadro’s Law Homework -- Page 480 -- 11, 13, 14bc, 15bc, 17, 19, 20.](https://reader035.fdocuments.us/reader035/viewer/2022062500/5697bfa61a28abf838c98316/html5/thumbnails/1.jpg)
January 31, 2008
• Go over homework
• Charles’s Law
• Avogadro’s Law
• Homework -- Page 480 -- 11, 13, 14bc, 15bc, 17, 19, 20
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Charles’s Law
Timberlake, Chemistry 7th Edition, page 259
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Charles's Law
If n and P are constant, then
V = (nR/P) = kTV = (nR/P) = kT
This means, for example, that Temperature goes up as Pressure goes up.
Jacques Charles(1746 - 1823)
Isolated boron and studied gases.Balloonist.
A hot air balloon is a good example of Charles's law.
VV and TT are directly related.
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• Raising the temperature of a gas increases the pressure if the volume is held constant.
• The molecules hit the walls harder.• The only way to increase the temperature at
constant pressure is to increase the volume.
Temperature
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• If you start with 1 liter of gas at 1 atm pressure and 300 K
• and heat it to 600 K one of 2 things happens
300 K
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• Either the volume will increase to 2 liters at 1 atm
300 K600 K
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300 K 600 K
the pressure will increase to 2 atm.
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Charles’s Law
Timberlake, Chemistry 7th Edition, page 259
![Page 9: January 31, 2008 Go over homework Charles’s Law Avogadro’s Law Homework -- Page 480 -- 11, 13, 14bc, 15bc, 17, 19, 20.](https://reader035.fdocuments.us/reader035/viewer/2022062500/5697bfa61a28abf838c98316/html5/thumbnails/9.jpg)
Charles’s Law
![Page 10: January 31, 2008 Go over homework Charles’s Law Avogadro’s Law Homework -- Page 480 -- 11, 13, 14bc, 15bc, 17, 19, 20.](https://reader035.fdocuments.us/reader035/viewer/2022062500/5697bfa61a28abf838c98316/html5/thumbnails/10.jpg)
The volume and absolute temperature (K) of a gas are directly related
–at constant mass & pressure
kT
VV
T
Charles’ Law
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Volume
(mL)
Temperature
(K)
V / T
(mL / K)
40.0
44.0
47.7
51.3
273.2
298.2
323.2
348.2
0.146
0.148
0.148
0.147
![Page 11: January 31, 2008 Go over homework Charles’s Law Avogadro’s Law Homework -- Page 480 -- 11, 13, 14bc, 15bc, 17, 19, 20.](https://reader035.fdocuments.us/reader035/viewer/2022062500/5697bfa61a28abf838c98316/html5/thumbnails/11.jpg)
The volume and absolute temperature (K) of a gas are directly related
–at constant mass & pressure
kT
VV
T
Charles’ Law
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
![Page 12: January 31, 2008 Go over homework Charles’s Law Avogadro’s Law Homework -- Page 480 -- 11, 13, 14bc, 15bc, 17, 19, 20.](https://reader035.fdocuments.us/reader035/viewer/2022062500/5697bfa61a28abf838c98316/html5/thumbnails/12.jpg)
Practice Problem – Charles’s Law
A child blows a soap bubble that contains air at 28 °C and has a volume of 23 cm3 at 1 atm. As the bubble rises, it encounters a pocket of cold air (temperature 10 °C). If there is no change in pressure, will the bubble get larger or smaller as the air inside cools to 18 °C? Calculate the new volume of the bubble.
2
2
1
1
T
V
T
V
C18
V
C28
cm23 23
K291
V
K301
cm23 23
V2 = 22 cm2
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Practice Problem – Charles’s Law
A sample of gas at 15 °C (at 1 atm) has a volume of 2.58 L. The temperature is then raised to 38 °C. Does the volume of the gas increase or decrease? What is the new volume?
2
2
1
1
T
V
T
V
C38
V
C15
L 2.58 2
K311
V
K288
L 2.58 2
V2 = 2.79 L
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Avogadro’s Law
• For a gas at constant temperature and pressure, the volume is directly proportional to the number of moles of gas
2
2
1
1
n
V
n
V
At constant temperature and pressureTemperature must be converted to Kelvin
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Avogadro’s Law
nn and VV are directly related.
This means, for example, that As the number of moles goes up volume goes up.
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Practice Problem – Avogadro’s LawSuppose we have a 12.2 L sample
containing 0.50 mol of oxygen gas, O2, at a pressure of 1 atm and a temperature of 25 °C. If all of this oxygen is converted to ozone, O3, at the same temperature and pressure, what will be the volume of the ozone formed?
2
2
1
1
n
V
n
V
3 O2 2 O3
32
32 Omol0.33
Omol3
Omol2xOmol0.50
mol0.33
V
mol0.50
12.2L 2
V2 = 8.1 L
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Practice Problem – Avogadro’s Law
A 1.5 mol sample of helium at a certain temperature and pressure has a volume of 31.4 L. A second sample of helium at the same temperature and pressure has a volume of 42.4 L. How many moles of helium are in the second sample?
2
2
1
1
n
V
n
V
2n
L42.4
mol1.5
L31.4
n2 = 2.03 mol