1. GASES: GASES: General Concepts Sherrie Park Per. ¾ AP Chemistry

2. General Concepts: Charles, Boyles, Avogadro, & the Ideal Gas Law Charle’s Law:Charle’s Law: states that if a given quantity of gas is held at a constant pressure, its volume is directly proportional to the absolute temperaturestates that if a given quantity of gas is held at a constant pressure, its volume is directly proportional to the absolute temperature As the temperature of the gas increases, the gas molecules will begin to move around more quickly and hit the walls of their container with more force—thus the volume will increaseAs the temperature of the gas increases, the gas molecules will begin to move around more quickly and hit the walls of their container with more force—thus the volume will increase V1/T1 = V2/T2V1/T1 = V2/T2

3. Boyle’s Law  states that the volume of a confined gas at a fixed temperature is inversely proportional to the pressure exerted on the gas. –This makes sense if you think of a balloon. When the pressure around a balloon increases, the volume of the balloon decreases, and likewise, when you decrease the pressure around a balloon, its volume will increase.

4.  Boyle’s law to can also be expressed in the following way, and this is the form of the law that you should memorize:  P1V1 = P2V2

5. Avogrado’s Law  The volume of a gas at a given temperature and pressure is directly proportional to the quantity of the gas.  Equal volumes of gases under the same conditions of temperature and pressure contain equal numbers of molecules.  V = constant n (where n is the number of moles of the gas)

6. IDEAL GAS LAW:  The ideal gas law is the most important gas law for you to know: it combines all of the laws previously.  The state of an amount of gas is determined by its pressure, volume, and temperature according to the equation: PV = nRT –P = Pressure (units: Atm, Pa, Torr, etc..) –V = Volume (units: L) –N = Moles (units: mols) –R = Gas Constant (depends on the units used in the formula) –T = Temperature (unit: Kelvin)

7.  An Ideal Gas is modeled on the Kinetic Theory of Gases which has 4 basic postulates –All gas particles are in constant, random motion. –All collisions between gas particles are perfectly elastic (meaning that the kinetic energy of the system is conserved). –The volume of the gas molecules in a gas is negligible. –Gases have no intermolecular attractive or repulsive forces. –The average kinetic energy of the gas is directly proportional to its Kelvin temperature and is the same for all gases at a specified temperature.

8.  Real Gases deviate from Ideal Gas Behaviour because –at low temperatures the gas molecules have less kinetic energy (move around less) so they do attract each other –at high pressures the gas molecules are forced closer together so that the volume of the gas molecules becomes significant compared to the volume the gas occupies