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KMT, Grahams Law & Real Gases. Kinetic Molecular Theory 1.Volume of individual particles is zero. 2.Collisions of particles with container walls cause.

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Presentation on theme: "KMT, Grahams Law & Real Gases. Kinetic Molecular Theory 1.Volume of individual particles is zero. 2.Collisions of particles with container walls cause."— Presentation transcript:

1 KMT, Grahams Law & Real Gases

2 Kinetic Molecular Theory 1.Volume of individual particles is zero. 2.Collisions of particles with container walls cause pressure exerted by gas.

3 Kinetic Molecular Theory 3.Particles exert no forces on each other. 4.Average kinetic energy Kelvin temperature of a gas.

4 Equations Related to KMT Kelvin temperature is an index of the random motions of gas particles (higher T means greater motion.) (The derivation of this equation can be found in many college physics texts)

5 Root Mean Square Speed Average velocity of the gas particles u RMS = (3RT/M) 1/2 M is in Kg R = J/K mol

6 Effusion: describes the passage of gas into an evacuated chamber. Diffusion: describes the mixing of gases. The rate of diffusion is the rate of gas mixing.

7 The Effusion of a Gas into an Evacuated Chamber

8 Diffusion: HCI(g) and NH 3 (g) Meet in a Tube

9 Grahams Law Diffusion: Effusion:

10 Real Gases Must correct ideal gas behavior when at high pressures and low temperatures - volume of molecules becomes significant -attractive forces become important

11 Gas at Low (a) and High (b) Concentration

12 Volume Taken up by Gas Particles

13 Plots of PV/nRT Versus P for Several Gases (200 K)

14 Plots of PV/nRT Versus P for Nitrogen Gas at Three Temperatures

15 Calculate the relative rates of diffusion of H 2(g) and Br 2(g) at the same conditions.

16 The rate of effusion of a particular gas was measured and found to be 24.0 mL/min. Under the same conditions, the rate of effusion of pure methane gas is 47.8 mL/min. What is the molar mass of the unknown gas?

17 Real Gases – van der Waals Equation corrected pressure corrected volume Van der Waals constants, a and b, are dependent on the type of gas molecule (see table 5.3)

18 Practice Problems Which gas will diffuse faster, ammonia (NH 3 ) or carbon dioxide (CO 2 )? What are their relative rates of diffusion? Freon-12 is used as a refrigerant in central home air- conditioners. The rate of effusion of Freon-12 to Freon-11 (molar mass = g/mol) is 1.07:1. The formula of Freon-12 is one of the following: CF 4, CF 3 Cl, CF 2 Cl 2, CFCl 3 or CCl 4

19 Answers 1.NH 3 diffuses 1.6 times faster 2. CF 2 Cl 2


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