CHEM 110 Lecture Notes - Lecture 13: Collision Frequency, Effusion, Molar Volume
Document Summary
Root mean square (rms) speed is related to both molar mass m of the gas and temperature t. When temperature increases, average kinetic energy increases, less molecules move slowly, and molecules move quickly, the rms speed increases. At the same t, different gases have the same average kinetic energy, but different rms speeds. On average: lighter gases move faster and heaver gases move slower. Effusion- leakage of gas through a small opening. Diffusion- even distribution of all gases throughout a volume of space. The rate of effusion and diffusion is not equal to the rms speed of the gas. But two rates measured under the same conditions for different gases will be proportional. Heavy molecules effuse and diffuse more slowly than lighter molecules. As altitude increases the number of molecules decreases, so number of collisions decreases -> pressure decreases. At the microscopic level, pressure depends on both the collision frequency and the average molecular speed.
