1. Combined Gas Law

2. Units first! Volume in liters, milliliters, or cm 3 Temperature must always be in KELVIN!!! Pressure can be in atmospheres, torr, or mm of Hg, or kilopascals (kPa) 1 atm = 760 torr = 760 mm Hg = 101.3 kPa

3. STP Stands for Standard Temperature and Pressure (see Ref Table A) 273 K 1 atm or 101.3 kPa

4. P1V1P1V1 P2V2P2V2 T1T1 T2T2 = Initial conditionsNew conditions

5. Gas law problems What volume will a gas occupy if the pressure on 244 ml of gas at 4 atm is increased to 6 atm? P 1 = 4 atm P 2 = 6 atm V 1 = 244 ml V 2 = ? T 1 = constant (1) T 2 = constant (1)

6. Set up equation and solve for unknown value 4 atm x 244 ml = 6 atm x V 2 1 1 4 x 244 = 6 x V 2 4 x 244 = V 2 = 160 ml 6

7. You try it! 75 ml of gas is at STP. What volume will the gas occupy if the temp is raised to 75 0 C and the pressure increased to 945 torr? CAREFUL! You must first convert temperature into Kelvin!