1. Warm-up 2H 2 (g) + O 2 (g)  2H 2 O (g) How many liters of water will be produced from 300 grams of Oxygen gas if Hydrogen gas is in excess? (at STP)

2. Gases, Day 8 Partial Pressure

3. Why do we use Kelvin? When you use Kelvin, you will never have a negative temperature! Absolute zero (the coldest temperature possible) occurs at 0 K

4. Gas Pressure In a mixture of gases, each gas has a partial pressure The pressure that the gas would have if it alone occupied the same volume and temperature as the mixture

5. Daltons Law of Partial Pressures The total pressure of a mixture is equal to the sum of all the partial pressures of each gas. P total = P 1 + P 2 + P 3 + …

6. Dalton’s Law Example What is the total pressure of a mixture of oxygen and hydrogen, if the partial pressure of oxygen is 4.5 atm and the partial pressure of hydrogen is 6.7 atm? Total pressure = 11.2 atm

7. Example What is the partial pressure of nitrogen in a mixture of nitrogen, hydrogen, and oxygen if the total pressure is found to be 20.76 atm and the partial pressure of oxygen is 7.5 atm and the partial pressure of hydrogen is 6.7 atm? N 2 Pressure = 20.76 – (7.5 + 6.7) = 6.56 atm

8. Example What is the total pressure of a mixture of CO 2 and O 2, if the partial pressure of oxygen is 145.5 kPa and the partial pressure of carbon is 6.7 atm?

9. Examples!! What is the partial pressure of nitrogen in a mixture of nitrogen, hydrogen, and oxygen if the total pressure is found to be 35.66 atm and the partial pressure of oxygen is 17.5 atm and the partial pressure of hydrogen is 7.45 atm? If I have a container that contains both oxygen and nitrogen, what’s the total pressure inside the container of the partial pressure of oxygen is 0.50 atm and the partial pressure of nitrogen is 0.75 atm?

10. What you can do with this… Given moles of specific gases, you can solve for individual pressures then add them up for the total pressure

11. Example 15 moles of nitrogen gas, 12 moles of oxygen gas, and 22 moles of hydrogen gas are mixed in a 25 liter flask at a temperature of 300 K. What are the partial pressures of each gas and the total pressure of the mixture? 1. Use the ideal gas law to find each gas’ partial pressure 2. Add up the pressures for the total pressure

12. What you can do with this… Given moles of specific gases, you can solve for individual pressures then add them up for the total pressure Using the combined gas law, you can determine the pressure of a mixture given initial conditions

13. Example The stopper between a 3.00 L bulb containing oxygen at 295 torr and a 1.00 L bulb containing nitrogen at 530 torr is opened. What is the total pressure of the mixture (assume constant T = 298 K)? P tot = P oxygen + P nitrogen You can treat each gas separately. After mixing, there will be the same number of moles of each gas, at the same T, just in a different volume.

14. What you can do with this… Given moles of specific gases, you can solve for individual pressures then add them up for the total pressure Using the combined gas law, you can determine the pressure of a mixture given initial conditions By comparing moles of each gas, as well as having a total pressure, you can calculate partial pressures

15. Example What is the partial pressure of each gas in a mixture which contains 40 g of He, 56 g of N 2, and 16 g of O 2, if the total pressure of the mixture is 5 atmospheres? 1. Convert each gas to moles 2. Determine the fraction of moles of each gas (mole of gas / total moles) 3. Multiply the fractions by the total pressure

16. Warm-up A mixture of hydrocarbons contains seven moles of methane, four moles of ethane, and three moles of propane. The container has a volume of 124 liters and the temperature is 22 °C. Find the partial pressures of the three gases, in atm.