KMT and Graham’s Law

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# KMT and Graham’s Law - PowerPoint PPT Presentation

KMT and Graham’s Law. Molecular Speed Of A Gas. Depends on the mass of the gas molecules and the temperature they are at R is in different units and has a different value ( R=8.3145) M is molar mass in kg/mole. Example. Find the speed of hydrogen gas at 25 o C.

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### KMT and Graham’s Law

Molecular Speed Of A Gas
• Depends on the mass of the gas molecules and the temperature they are at

R is in different units and has a different value ( R=8.3145)

M is molar mass in kg/mole

Example
• Find the speed of hydrogen gas at 25o C.
• Find the speed of oxygen gas at 25o C.
Effusion
• Gas escapes through tiny holes when a pressure difference is present
Diffusion
• Gases will mix uniformly
Graham’s Law
• Rate of both effusion and diffusion is inversely related to the square root of their weights
• Shows the relationship between rate and molecular weight
Example
• If an unknown gas effuses at a rate that is only .468 times that of oxygen at the same temperature, what is its molecular weight?
Ideal vs. Real Gas Behavior
• Ideal gases follow all of the gas laws outlined
• No gas is totally ideal, but at low pressures and/or high temperatures most come close
• Gases will deviate significantly from ideal at high pressures and/or low temperatures

- particles become closer together and intermolecular forces between significant