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Applied Physics and Chemistry. Gases Lecture 5: Combined Gas Law. Ideal Gas Law. Relates and combines all the other gas laws Mathematical relation of pressure, temperature, volume and the number of moles of a gas PV = nRT R is the universal gas constant. Ideal Gas Constant.
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Applied Physics and Chemistry Gases Lecture 5: Combined Gas Law
Ideal Gas Law • Relates and combines all the other gas laws • Mathematical relation of pressure, temperature, volume and the number of moles of a gas • PV = nRT • R is the universal gas constant
Ideal Gas Constant • R= 0.08204784 Latmo/moleK • Watch the units!
Ideal Gas Law • Allows us to find a fourth property if we know 3 of the properties of the gas • Based on experimental measurements • Gas that obeys this law is an ideal gas • Most gases are ideal unless they are at very high pressure or very low temperature
Sample Problem • What is the pressure in atmospheres exerted by 0.500 mole sample of nitrogen gas in a 10.0 L container at 298 K? • Known: V=10.0 L n=0.500 mole T=298 K R=0.08205784 Latmo/moleK • PV=nRT solve for P: P=nRT/V • P=(0.500 mole)(0.08205784 Latmo/moleK)(298K) 10.0 L • P=1.22661816 atmo = 1.23 atmo
Sample Problem • What is the volume of 0.250 mole of oxygen gas at 20.0oC and 0.974 atmo pressure? • Known: 0.250 mole=n T=293.13K P=0.974 atmo R=0.08205784 Latmo/moleK • PV=nRT solve for V: V=nRT/P • V=(0.250 mole)(0.08205784 Latmo/moleK)(293 K) 0.974 atmo • V=6.171187659 L = 6.17 L
Sample Problem • What mass of chlorine gas in grams is contained in a 10.0 L tank at 27oC and 3.50 atmo pressure? • Known: V=10.0L T=300.15 K P=3.50 atmo • PV=nRT n: n=PV/RT • n= (3.50 atmo)(10.0L) (0.08205784 Latmo/moleK)(300.15K) • n = 1.42 mole • Mass: 1.42 mole Cl2 x 70.906 g = 100.7 g • 1 mole
Combined Gas Law • Combines gas laws • PV/T=k • Since we normally compare: • P1V1 = P2V2 T1 T2
Sample Problem • A helium-filled balloon has a volume of 50.0 L at 25oC and 1.08 atmo. What volume will it have at 0.855 atmo and 10oC?