1. Grams to Moles to Molecules

2. How many molecules in 5.00g of hydrogen gas? 5.00g H 2 x 1mole x 6.02 x 10 23 molecules = 2.02 g1 mole = 5.00 / 2.02 x 6.02 x 10 23 = 1.37 x 10 24 molecules

3. Mole Diagram Moles Grams Molecules Divide by MM multiply by Avogadros’s # Divide by Avogadros’s # Multiply by MM

4. Example Problems 1.How many molecules in 3.1 grams of CH 4 ? 3.1 g CH 4 x 1 mole x 6.02 x 10 23 molecules = 16.04 g 1 mole = 1.16 x 10 23 molecules How many atoms of Hydrogen are there? 1.16 x 10 23 molecuels x 4 atoms of H = = 4.64 x 10 23 atoms of H

5. Example Problems 2.How many grams in 6.04 x 10 24 molecules of O 2 ? 6.04 x 10 24 molecules x 1 mole x 32.00 g 6.02 x 10 23 molecules1 mole = 321 grams of O 2

6. Molar Volume The molar volume of a gas is measured at STP (standard temperature and pressure). The Molar Volume is 22.4 L for 1mole of any gas. Molar V = 22.4 L/mol

7. 1 mole of gas = 6.02 x 10 23 molecules 6.02 x 10 23 molecules of any gas at STP will occupy 22.4 L (Avogadro’s principle) Allows you to interrelate mass, moles, pressure, volume, and temperature for any sample of gas.

8. Molar Volume as a Conversion Factor The molar volume at STP can be used to form conversion factors. What is the volume occupied by 2.75 moles N 2 gas at STP? The molar volume is used to convert moles to liters. 2.75 moles N 2 x 22.4 L = 61.6 L 1 mole

9. Learning Check 1. What is the volume at STP of 4.00 g of CH 4 ? a) 5.60 L b) 11.2 L c) 44.8 L 2. How many grams of He are present in 8.00 L of He at STP? a) 25.6 g b) 0.357 g c) 1.43

10. Solution 1. 4.00 g CH 4 x 1 mole CH 4 x 22.4 L (STP) = 5.60 L 16.0 g CH 4 1 mole CH 4 2. 8.00 L x 1 mole He x 4.00 g He = 1.43 g He 22.4 L 1 mole He