Gases and the Kinetic Molecular Theory
Speeds of gas molecules. For a single molecule. Kinetic energy is: KE = ½ mv2 m = mass; v = velocity For a collection of gas molecules, the average kinetic energy is: R = ideal gas constant = 8.314 J/Kmol T = temperature in Kelvin
How fast do gas molecules move? Called the root mean square speed of the gas. in kg/mol Equation gives speed in meters/second. What is the rms speed of O2 molecules at room temperature?
Boltzmann Distributions
Boltzmann Distributions and Molar Mass
Boltzmann Distributions and Temperature
Gas Diffusion
Gas Effusion
Graham’s Law of Gas Effusion: used for determining molar mass of a gas
Example: A sample of ethane, C2H6, effuses through a small hole at a rate of 3.6 x 10-6 mol/hr. An unknown gas, under the same conditions, effuses at a rate of 1.3 x 10-6 mol/hr. Calculate the molar mass of the unknown gas.