Warm-upWarm-up

1. 1. What formula will you use if you What formula will you use if you are given volume and pressure?are given volume and pressure?

2. A sample of gas at 47°C and 2. A sample of gas at 47°C and 1.03 atm occupies a volume of 1.03 atm occupies a volume of 2.20 L. What volume would this 2.20 L. What volume would this gas occupy at 107°C and 0.789 gas occupy at 107°C and 0.789 atm?atm?

Motion of gas particlesMotion of gas particles

Two types:Two types:– Diffusion – gradual mixing or Diffusion – gradual mixing or

spreading out of a gasspreading out of a gas– Effusion – molecules confined in a Effusion – molecules confined in a

container randomly pass though a container randomly pass though a small opening in the containersmall opening in the container

Motion of gas particlesMotion of gas particles

The rate (speed) of diffusion and The rate (speed) of diffusion and effusion depends on the mass or effusion depends on the mass or size of the moleculessize of the molecules

Lighter molecules move faster Lighter molecules move faster than heavier moleculesthan heavier molecules

Avogadro’s LawAvogadro’s Law

Says that equal volumes of gases Says that equal volumes of gases at same temp and pressure at same temp and pressure contain the same number of contain the same number of moleculesmolecules

Led to the discovery of the Ideal Led to the discovery of the Ideal Gas LawGas Law

Ideal Gas LawIdeal Gas Law

Relationship between pressure, volume, Relationship between pressure, volume, temp, and number of moleculestemp, and number of molecules

PV = nRTPV = nRT

n = number of moles n = number of moles R = Ideal Gas Constant = 0.082R = Ideal Gas Constant = 0.082

UnitsUnits

Pressure - atmPressure - atm Volume - LitersVolume - Liters Temperature - KelvinTemperature - Kelvin n - molesn - moles

ExampleExample

What is the pressure in atm exerted What is the pressure in atm exerted by a 0.500 mol sample of nitrogen by a 0.500 mol sample of nitrogen gas in a 10.0 L container at 298 K?gas in a 10.0 L container at 298 K?

P=??P=?? V=10.0 LV=10.0 L n=0.500 moln=0.500 mol R=0.082(constant)R=0.082(constant) T=298 KT=298 K

ExampleExample

PV=nRTPV=nRT

P(10.0) = (0.500)(0.0821)(298)P(10.0) = (0.500)(0.0821)(298)

P = P = (0.500)(0.0821)(298)(0.500)(0.0821)(298) = 1.22 = 1.22 atmatm

(10.0)(10.0)

Graham’s LawGraham’s Law

The rate of effusion of gas is The rate of effusion of gas is inversely proportional to the inversely proportional to the square root of its formula masssquare root of its formula mass