The document discusses calculating quantities of substances involved in chemical reactions using moles. It defines terms like relative atomic mass and explains that 1 mole of any substance has a mass in grams equal to its relative formula/molecular mass. Examples demonstrate using chemical equations and molar masses to determine the mass of products formed from given masses of reactants.

3. How heavy is a mole? The mass of 1 mole of a substance varies. It depends on its RAM or RMM. 1 mole of carbon has a mass of 12g but 1 mole of oxygen would have a mass of 32g. We can work out how many moles of a substance we have by dividing mass by RAM/RMM. Mass (g) RAM/RMM moles

4. Moles are useful because they help us work out how much of something we might make or need. E.g. what mass of CO is made if you burn carbon with 16g of O 2 ? Write an equation: 2C + O 2  2CO The equation tells us how many moles of everything there is: 2 moles of C + 1 mole of O 2  2 moles of CO Now work out how many moles you have of O 2 (it has to be O 2 because this is the only substance you are told anything about): Moles of O 2 = mass/RMM = 16/32 = 0.5 mol Now use the equation to work out how many moles of CO you would make: If there was 1 mole of O 2 there would be 2 moles of CO so moles of CO = moles O 2 x 2 = 1 mol Now convert the numbers of moles you have to mass: Mass of CO = moles x RMM = 1 x (12+16) = 28g

5. What mass of iron is needed to make 16g of iron (III) oxide? Write an equation: 4Fe + 3O 2  2Fe 2 O 3 The equation tells us how many moles of everything there is: 4 moles of Fe + 3 moles of O 2  2 moles of Fe 2 O 3 Now work out how many moles you have of Fe 2 O 3 (it has to be Fe 2 O 3 because this is the only substance you are told anything about): Moles of Fe 2 O 3 = mass/RMM = 16/160 = 0.1 mol Now use the equation to work out how many moles of CO you would make: If there was 2 moles of Fe 2 O 3 there would be 4 moles of Fe so moles of Fe = moles Fe 2 O 3 x 2 = 0.2 mol Now convert the numbers of moles you have to mass: Mass of Fe = moles x RMM = 0.2 x 56 = 11.2g