1. Unit 5A Chapter 10: Chemical Quantities Mole-Mass Relationships ABClark-Grubb

2. Mole – Mass Relationships Use the molar mass of an element or compound to convert between mass and moles of a substance Converting Moles to Mass Calculate Molar Mass First Al = 27.0 g O = 16.0 g X 2 X 3 = 54.0 g/mol = 48.0 g/mol + 102.0 g/mol 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 rounded to the correct SIG FIGS How many grams are in 9.45 mol Al 2 O 3 ?

3. Converting Mass to Moles Calculate Molar Mass Fe = 55.8 g O = 16.0 g X 2 X 3 = 111.6 g/mol = 48.0 g/mol + 159.6 g/mol 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 rounded to SIG FIGS How many moles are in 92.2 g of Fe 2 O 3 ?

4. Try this… 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/mol = 42.0 g/mol + 282.0 g/mol 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 rounded to SIG FIGS

5. Try this … Calculate the number of moles in 75.0 g of magnesium fluoride.* Calculate Molar Mass Mg = 24.3 g F = 19.0 g X 1 X 2 = 24.3 g/mol = 38.0 g/mol + 62.3 g/mol 75.0 g MgF 2 1 mol MgF 2 62.3 g MgF 2 = 1.20385 mol MgF 2 = 1.20 mol MgF 2 rounded to SIG FIGS *Use your common ion table, find the formula. MgF 2