ACTUALLYmake this much % YIELD is the amount of product you actually make as a % of the amount you should theoretically make PRODUCT REACTANTS % YIELD ABOUT 75% + ACTUALLYmake this much SHOULD make this much

Yield The %YIELD is the amount of chemical that is produced during a reaction. Percentage = Actual Yield x 100 Yield Predicted Yield

Calculating percentage yield I reacted copper sulphate solution with some iron. Using reacting masses, I worked out that the theoretical yield of the reaction was 50 grams of copper. I lost some copper when I filtered the solution and ended up with 40 grams. What is the percentage yield of my reaction? percentage yield = x 100 actual yield theoretical yield percentage yield = x 100 = 80% 40 g 50 g

2Mg + O2 → 2MgO MgCO3 → MgO + CO2 Atom Economy Compare these two industrial reactions: Desired product MgO 2Mg + O2 → 2MgO Which method do you think chemists in industry prefer to use? Why? MgCO3 → MgO + CO2

Stuff you also get but don’t want ATOM ECONOMY is the mass of the product you want as a % of the mass of all the products you make REACTANTS PRODUCTS + Stuff you also get but don’t want Stuff you want ATOM ECONOMY about 50%

CaCO3 = CaO + CO2 RFM: 100 56 44 CALCULATING ATOM ECONOMY Often, chemical reactions produce unwanted products along with the product you want. ATOM ECONOMY is the mass of product you want as a % of the mass of all the products you make Waste product Useful product CaCO3 = CaO + CO2 RFM: 100 56 44 ATOM ECONOMY mass useful product mass of all products = X 100% Atom Economy = 56 / (56 + 44) = 56 / 100 = 56 %

2Mg + O2 → 2MgO Fe2O3 + 3CO → 2Fe + 3CO2 RFM: 48 32 80 160 84 112 132 ATOM ECONOMY is the mass of product you want as a % of the mass of all the products you make RAM Mg 24 Fe 56 C 12 O 16 2Mg + O2 → 2MgO RFM: 48 32 80 Atom Economy = 80 / 80 x 100% = 100 % (obviously) Fe2O3 + 3CO → 2Fe + 3CO2 160 84 112 132 Atom Economy = 112 / 244 x 100% = 45.9 %

2CuO + C  2Cu + CO2 CuS + O2 Cu + SO2 RFM 128 44 RFM 64 64 = = Find the atom economy for these 2 methods of extracting copper: 2. Heat copper sulphide with oxygen 1. Heat copper oxide with carbon RAM Cu 64, O 16, C 12, S 32 2CuO + C  2Cu + CO2 CuS + O2 Cu + SO2 RFM 128 44 RFM 64 64 Mass of all products = 64 + 64 = 128 Mass of all products 128 + 44 = 172 Mass of copper = 64 Mass of copper = 128 ATOM ECONOMY 128 172 X 100 = ATOM ECONOMY 64 128 X 100 = = 74.4 % = 50 %

Real example: Paracetamol The non-prescription analgesic market (paracetamol, aspirin, ibuprofen) is worth about £21 billion annually. Maximising % yield and atom economy in the reactions at left is vital to save money and conserv energy and resources

Stuff you also get but don’t want ACTUALLY make this much SUMMARY % YIELD is the amount of product you actually make as a % of the amount you should theoretically make ATOM ECONOMY is the mass of the product you want as a % of the mass of all the products you make % YIELD ABOUT 75% Stuff you also get but don’t want Stuff you want ATOM ECONOMY about 50% ACTUALLY make this much SHOULD make this much

CHEMICAL ENGINEERS must plan to maximise: Raw materials are scarce and expensive and so must be carefully conserved. Also, chemical processes need to produce as little waste as possible, minimise costs, energy use and pollution. CHEMICAL ENGINEERS must plan to maximise: PERCENTAGE YIELD by… ATOM ECONOMY by… Choosing the most EFFICIENT REACTION to make the product to… Using the most EFFICIENT REACTION CONDITIONS & APPARATUS to… Reduce energy use, costs and conserve raw materials Reduce waste and pollution