1 / 18

Gases

Learn about Graham’s Law, diffusion, and effusion in gases, including mathematical applications and real-world examples. Understand the behavior of gases and how to calculate molecular speeds.

cturpin
Download Presentation

Gases

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Gases

  2. GASES manometers pressure Kinetic theory of gases Units of pressure Behavior of gases Partial pressure of a gas Pressure vs. volume Pressure vs. temperature Temperature vs. volume Diffusion/effusion Combined gas law Ideal gas law

  3. Diffusion and Effusion • Diffusion • The gradual mixing of 2 gases due to random spontaneous motion • Effusion • When molecules of a confined gas escape through a tiny opening in a container

  4. Graham’s Law

  5. Graham’s Law • Conceptual: • Lighter gases travel quicker at the same temp • Consider H2 vs. Cl2 Which would diffuse at the greater velocity?

  6. Graham’s Law • Calculating the speed of a molecule can be done using the following equation

  7. Graham’s Law • Calculate the rms speed of an N2 molecule at 25oC • Convert temp to Kelvin • MM = 28 • R= 8.314 J/mol.K ( 0.0821 x 101.3)

  8. Graham’s Law • The relative rates of diffusion of two gases vary inversely with the square roots of the gram formula masses. • Mathematically:

  9. Graham’s Law Problem • A helium atom travels an average 1000. m/s at 250oC. How fast would an atom of radon travel at the same temperature? • Solution: • Let rate1 = x rate2 = 1000. m/s • Gfm1 = radon 222 g/mol • Gfm2 = helium = 4.00 g/mol

  10. Solution (cont.) • Rearrange: • Substitute and evaluate:

  11. Applications of Graham’s Law • Separation of uranium isotopes • 235U • Simple, inexpensive technique • Used in Iraq in early 1990’s as part of nuclear weapons development program • Identifying unknowns • Use relative rates to find gfm

  12. Problem 2 • An unknown gas effuses through an opening at a rate 3.16 times slower than that of helium gas. What is the gfm of this unknown gas?

  13. Solution • Let gfm2 = x rate2 = 1 gfm1 = 4.00 rate1 = 3.16 • From Graham’s Law,

  14. Solution, cont. • Rearrange • Substitute and evaluate:

  15. WWWW we do • What is the rms speed of an He atom at 40oC

  16. The rate of effusion was measured for an unknown gas is 10 time slower than helium so • Runknown /R He = 0.1 what is the molecular mass of the unknown gas

More Related