1. Chapter 10: Chemical Quantities Mole-Mass Relationships Mrs. Mansberger

2. Converting Mass to Moles Known 92.2 g Fe 2 O 3 Unknown ? mol Fe 2 O 3 Calculate Molar Mass Fe = 55.8 g O = 16.0 g X 2 X 3 = 111.6 g = 48.0 g + 159.6 g 159.6 g Fe 2 O 3 = 1 mol Fe 2 O 3 92.2 g Fe 2 O 3 1 mol Fe 2 O 3 159.6 g Fe 2 O 3 = 0.577694 mol Fe 2 O 3 = 0.578 mol Fe 2 O 3 Use the molar mass of an element or compound to convert between mass and moles of that substance

3. Try this with your partner… Calculate the number of moles in 75.0 g of magnesium fluoride. Known 75.0 g MgF 2 Unknown ? mol MgF 2 Calculate Molar Mass Mg = 24.3 g F = 19.0 g X 1 X 2 = 24.3 g = 38.0 g + 62.3 g 62.3 g MgF 2 = 1 mol MgF 2 75.0 g MgF 2 1 mol MgF 2 62.3 g MgF 2 =1.20385 mol MgF 2 = 1.20 mol MgF 2

4. Mole – Mass Relationships Converting Moles to Mass Known 9.45 mol Al 2 O 3 Unknown ? g Al 2 O 3 Calculate Molar Mass First Al = 27.0 g O = 16.0 g X 2 X 3 = 54.0 g = 48.0 g + 102.0 g 102.0 g Al 2 O 3 = 1 mol Al 2 O 3 9.45 mol Al 2 O 3 102.0 g Al 2 O 3 1 mol Al 2 O 3 =963.9 g Al 2 O 3 = 964 g Al 2 O 3

5. Try this with your partner… Known 0.452 mol C 20 H 42 Unknown ? g C 20 H 42 Calculate Molar Mass C = 12.0 g H = 1.0 g X 20 X 42 = 240.0 g = 42.0 g + 282.0 g 282.0 g C 20 H 42 = 1 mol C 20 H 42 0.452 mol C 20 H 42 282.0 g C 20 H 42 1 mol C 20 H 42 = 127.464 g C 20 H 42 = 127 g C 20 H 42