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

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 = g = 48.0 g g g Fe 2 O 3 = 1 mol Fe 2 O g Fe 2 O 3 1 mol Fe 2 O g Fe 2 O 3 = mol Fe 2 O 3 = mol Fe 2 O 3 Use the molar mass of an element or compound to convert between mass and moles of that substance

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 g 62.3 g MgF 2 = 1 mol MgF g MgF 2 1 mol MgF g MgF 2 = mol MgF 2 = 1.20 mol MgF 2

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 g g Al 2 O 3 = 1 mol Al 2 O mol Al 2 O g Al 2 O 3 1 mol Al 2 O 3 =963.9 g Al 2 O 3 = 964 g Al 2 O 3

Try this with your partner… Known 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 = g = 42.0 g g g C 20 H 42 = 1 mol C 20 H mol C 20 H g C 20 H 42 1 mol C 20 H 42 = g C 20 H 42 = 127 g C 20 H 42