Kinetic Molecular Theory

1. Kinetic Molecular Theory Chemistry Semester II Notes for Gas Laws

2. Kinetic Molecular Theory • Based on the assumption that all gases behave like an “ideal gas”. • Ideal gas particles are so small that the volume of the particles is essentially zero in relation to the total volume of the gas. • Ideal gas particles are in constant random motion. • Ideal gas molecules move in straight lines until they collide with other particles.

3. KMT continued • Ideal gas molecules have no attractive or repulsive forces. • Collisions between ideal gas molecules are elastic (no energy lost, just transferred between molecules). • Average kinetic energy of an Ideal gas molecule is directly proportional to the absolute temperature (measured in K) ALWAYS USE KELVIN TO MEASURE TEMPERATURE!!! K = O C + 273

4. KMT continued • Four variables describe the actions of a gas particle: • Volume (V) • SI unit: Liters (L) • 1L = 1dm3 = 1000cm3 = 0.001m3 • Temperature (T) • Directly proportional to kinetic energy ( KE = ½ mv2 , where v = velocity) • SI unit: K (Kelvin) • 0o C = 273 K

5. KMT • Pressure (P) • Measures the number of collisions of molecules with its container • force/unit area • Manometers or barometers are used to measure • SI unit: kPa (kilopascals) • 101.3kPa = 1 atm = 760 mm of Hg = 760 torr = 14.7psi • Number of moles (n) • Can be used to solve for molecular masses • Can be used to solve for gram amounts of gases • 1 mol of gases occupies 22.4L volume at STP, called the Molar Volume

6. KMT • The Kinetic Molecular Theory assumes gases are at STP • Laboratory experiments rarely performed at STP • Corrections are necessary for this problem • STP is 273K = 0 °C and 1 atmosphere