1. Due: Behavior of Gases WS Today: Gas Laws Boyles, Charles, Combined, Dalton HW Gas Laws Practice Problems

2. Warm Up What are the four variables that affect gases? What is STP (identify the values and units)

3. The Gas Laws The gas laws are mathematical equations that describe the behavior of gases as they are mixed, subjected to changes in pressure, temperature, volume, or amount.

4. Graphic Organizer in notes Make a table Name of Law DefinitionVariables Held Constant Variables that Change Equations

5. Pressure, Temperature, and Volume Relationships Mathematical equations relating the pressure, temperature, and volume of gases are called gas laws.

6. Pressure and Volume Lecture PLUS Timberlake 20006

7. Boyle’s Law Boyle's law—describes the pressure and volume behavior of a gas sample that is maintained at constant temperature. Boyle's law Pressure and volume are inversely related Pressure and volume This relationship leads to the following equation: P 1 V 1 = P 2 V 2

8. Boyle’s Law Example If you have 5.6L of a gas in a piston at a pressure of 1.5 atm and compress the gas until it’s volume is 4.8L what will the new pressure inside the piston be? Determine Law to use by identifying variables Write what you know

9. Volume and temperature Lecture PLUS Timberlake 20009

10. Charles’s Law Charles’s Law Cont. The volume of gas increased linearly with temperature provided the PRESSURE remains constantvolume of gas V 1 = V 2 T 1 T 2 Temperature must be in K Balloons in liquid nitrogen

11. Example for Charles’s Law 1.If temperature of a gas increases from 200K to 400K what is the resulting volume of the gas? 2. If a balloon contains 45L of Helium at 25°C and the temperature of the balloon increases to 55°C, what will now be the volume of the balloon?

12. The Combined Gas Law Gay-Lusacs Law – Inverse Relationship between Pressure and Temperature (increase pressure, decrease temperature) P 1 = P 2 T 1 T 2 Combined Gas Law – one equation which combines all the gas laws together.

13. Example Problem The volume of a gas filled balloon is 30.0L at 40C and 153kPa pressure. What volume will the balloon have at standard temperature and pressure?

14. Gas Law Examples A gas sample has a volume of 2.50 liters when it is at a temperature of 30.0ºC and a pressure of 1.80 atm. What volume, in liters, will the sample have if the pressure is increased to 3.00 atm, and the temperature is increased to 100ºC? A gas occupies 3.8 L at 0.70 atm. If the volume is expanded, at a constant temperature, to 6.5 L, then what is the final pressure? A constant volume of oxygen gas, O 2, is heated from 120 o C to 212 o C. The final pressure is 20.3 atm. What was the initial pressure?

15. Dalton’s Law According to Dalton's law, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the gases in the mixture. P total = P 1 + P 2 + P 3 + … or

16. Partial Pressure The partial pressure of an individual gas of a mixture is the pressure the gas would exert if it were alone in the container at the same temperature as the mixture as shown in the following illustration:

17. Partial Pressures When one collects a gas over water, there is water vapor mixed in with the gas. To find only the pressure of the desired gas, one must subtract the vapor pressure of water from the total pressure. P gas = P tot – P water

18. Example Problems Air contains oxygen, nitrogen, carbon dioxide, and trace amounts of other gases. What is the partial pressure of oxygen? The total pressure is 101.30 kPa and the partial pressures of nitrogen is 79.10 kPa, carbon dioxide is 0.040 kPa, and other gases are 0.94kPa.