Grams to Moles to Molecules

1. Grams to Moles to Molecules

2. Grams to Moles to Molecules • How many molecules in 5.00g of hydrogen gas? 5.00g H2 x 1mole x 6.02 x 1023 molecules = 2.02 g 1 mole = 5.00 / 2.02 x 6.02 x 1023 = 1.37 x 1024 molecules

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

4. Example Problems • How many molecules in 3.1 grams of CH4? 3.1 g CH4 x 1 mole x 6.02 x 1023 molecules = 16.04 g 1 mole = 1.16 x 1023 molecules How many atoms of Hydrogen are there? 1.16 x 1023 molecuels x 4 atoms of H = = 4.64 x 1023 atoms of H

5. Example Problems • How many grams in 6.04 x 1024 molecules of O2? 6.04 x 1024molecules x 1 mole x 32.00 g 6.02 x 1023molecules 1 mole = 321 grams of O2

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 1023 molecules • 6.02 x 1023 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 ConversionFactor The molar volume at STP can be used to form conversion factors. • What is the volume occupied by 2.75 moles N2 gas at STP? • The molar volume is used to convert moles to liters. 2.75 moles N2 x 22.4 L = 61.6 L 1 mole

9. Learning Check 1. What is the volume at STP of 4.00 g of CH4? 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 CH4 x 1 mole CH4 x 22.4 L (STP) = 5.60 L 16.0 g CH4 1 mole CH4 2. 8.00 L x 1 mole He x 4.00 g He = 1.43 g He 22.4 L 1 mole He