gases. copyright © houghton mifflin company. all rights reserved.chapter 5 | slide 2 why study...
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GASES
Copyright © Houghton Mifflin Company. All rights reserved.Chapter 5 | Slide 2
Why study gases?
• An understanding of real world phenomena.
• An understanding of how science “works.”
Copyright © Houghton Mifflin Company. All rights reserved.Chapter 5 | Slide 3
A Gas
• Uniformly fills any container.
• Mixes completely with any other gas.
• Exerts pressure on its surroundings.
5.1
Copyright © Houghton Mifflin Company. All rights reserved.Chapter 5 | Slide 4
Pressure
• Equal to force/unit area
• SI units = Newton/meter2 = 1 Pascal (Pa)
• 1 standard atmosphere = 101,325 Pa
• 1 standard atmosphere = 1 atm = 760 mm Hg = 760 torr = 101.3 kPa
5.1
Copyright © Houghton Mifflin Company. All rights reserved.Chapter 5 | Slide 5
Volume and Temperature
• What law results from observations like these?
• The volume of a gas depends on the temperature of the gas (constant P and n).
5.2
Copyright © Houghton Mifflin Company. All rights reserved.Chapter 5 | Slide 6
Charles’s Law
• Volume and Temperature (in Kelvin) are directly related (constant P and n).
• Charles’s Law: V=bT
• K = °C + 273
• 0 K is called absolute zero
5.2
Figure 5.17 The Effects of Increasing the Temperature of a Sample of Gas at
Constant Pressure
Copyright © Houghton Mifflin Company. All rights reserved.Chapter 5 | Slide 8
Other Laws
• Pressure and Volume are inversely related (constant T and n)
• Boyle’s Law: PV = k
5.2
As Pressure Increases, the Volume of SO2 Decreases
As Pressure Increases, the Volume Decreases
Copyright © Houghton Mifflin Company. All rights reserved.Chapter 5 | Slide 11
Other Laws
• Volume and number of moles are directly related (constant T and P)
• Avogadro’s Law: V = an
5.2
Figure 5.18 Increased Volume due to Increased Moles of Gas at Constant
Temperature and Pressure
Copyright © Houghton Mifflin Company. All rights reserved.Chapter 5 | Slide 13
Ideal Gas Law
• We can bring all of these laws together into one comprehensive law:
V = bTPV = kV = an
5.3
Copyright © Houghton Mifflin Company. All rights reserved.Chapter 5 | Slide 14
Ideal Gas Law
• We can bring all of these laws together into one comprehensive law:
PV = nRT(where R = 0.08206 L·atm/mol·K)
5.3
Copyright © Houghton Mifflin Company. All rights reserved.Chapter 5 | Slide 15
p is the absolute pressure of the gas,V is the volume of the gas,n is the number of moles of gas,R is the universal gas constant,T is the absolute temperature.