1. Molar Volume

2. Avagadro’s Principle Equal volumes of gases contain equal numbers of molecules Volume of a gas varies directly with the number of molecules if pressure and temperature stay constant

3. Standard Molar Volume Volume occupied by 1 mole of a gas at STP 22.414 L/mole One mole of any gas occupies 22.414 L at STP

4. Examples What volume will 3.75 moles of O 2 occupy at STP? How many moles in 1.5 L of H 2 at STP?

5. Examples A chemical reaction produced 45.0ml of Nitrogen gas at STP. What is the mass of the gas produced? What volume will 88g of carbon dioxide occupy at STP?

6. Partial Pressure In a mixture of gases, the total pressure of the mixture is the sum of the pressures of each gas P air = P nit + P ox + P H + …..

7. We can find out the pressure in the fourth container. By adding up the pressure in the first 3. 2 atm 1 atm 3 atm 6 atm

8. Gas Collection When pure gases are collected over water, some water vapor will be present in the gas The total pressure of the gas is equal to the pressure of the gas plus the pressure of the water vapor P T = P G + P wat

10. Pressure of Water Vapor Depends on the Temp

11. Example A gas is collected over water on a day where the atmospheric pressure is 755mmHg and the temp is 20°C. What is the partial pressure of the gas?