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# Chpt 5 - Gases - PowerPoint PPT Presentation

Chpt 5 - Gases. Gas Law Development Dalton’s Partial pressure law Graham’s effusion Kinetic Theory Root-mean-square velocity van der Waals equation of state HW: Chpt 5 - pg 119-128, #s 5, 22, 23, 25, 31, 32, 35, 39, 41, 46, 55, 64, 66, 71, 75, 77, 81, 91, 95, 97, 101, 124 Due Mon 9/28.

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Presentation Transcript

• Gas Law Development

• Dalton’s Partial pressure law

• Graham’s effusion

• Kinetic Theory

• Root-mean-square velocity

• van der Waals equation of state

• HW: Chpt 5 - pg 119-128, #s 5, 22, 23, 25, 31, 32, 35, 39, 41, 46, 55, 64, 66, 71, 75, 77, 81, 91, 95, 97, 101, 124 Due Mon 9/28

Pressure is? Units?

The height in mm of mercury

above the surface of the resevoir

of mercury determines the pressure.

The units are mmHg.

mmHg is also the same unit as

Torr. i.e. standard pressure is 760 mmHg and 760 Torr

Similar to the barometer,

the height difference of the Hg relates the pressure difference in the unknown gas bulb side to the current atmospheric pressure.

The higher Hg side has the _____ pressure.

(higher/lower)

• Constant temperature experiments demonstrated the PV=constant graphing this yields an inverse relationship

• Thus if the pressure of volume changes at a constant temperature

P1V1 = P2V2

• Constant pressure experiments demonstrated that Volume is directly proportional to Temperature (Kelvin)

V1 = V2

T1 T2

• Several gases were used & all extrapolate to zero volume and the same temperature at negative 273oC

Charles’s Law

Experiment results

P1V1 = P2V2

T1 T2

Avogadro’s Law - equal volumes of gas contain equal particles of gas

V = k n

At constant temperature and pressure the volume is directly proportional to the number of moles of gas.

• Putting it all together, we can calculate that constant now. The universal gas constant R.

PV=R or PV=nRT

nT R =0.0821 l*atm/mol*K

=8.31 l*kpa/mol*K

If more than one type of gas or more than one isotope, which gas effuses faster?

Lighter gas moves

Faster!!

KE = 1/2 mv2

Relative Molecular Speed Distribution of H2 and UF6

Diffusion Rates of NH3and HCl Molecules Through Air

Plots of PV/nRT vs. P for Several Gases

Values of the van der Waals Constants for Common Gases