HIGHER GRADE CHEMISTRY CALCULATIONS

1. 360 399.9 percentage yield = x 100 = 90.0% HIGHER GRADE CHEMISTRY CALCULATIONS Percentage yield is calculated using the formula:- percentage yield = x 100 The actual yield is given in the question. The theoretical yield is calculated from the balanced equation. actual yield theoretical yield Calculation of percentage yield. Worked example. In a reaction 320 kg of sulphur dioxide reacted with oxygen to form 360kg of sulphur trioxide. Calculate the percentage yield. Find the theoretical yield using the balanced equation:- 2SO2 + O2 2SO3 2 mol  2 mol 128.2 g  160.2 g 128.2 kg  160.2 kg 320 kg  399.9 kg

2. 0.66 2.83 percentage yield = x 100 = 23.32% Calculation of percentage yield. • Calculations for you to try. • 0.5 tonnes of hydrogen reacts with excess nitrogen to form • 0.66 tonnes of ammonia. • N2 + 3H2 2NH3 • Calculate the percentage yield of ammonia. N2 + 3H2 2NH3 3 mol  2 mol 6 g  34 g 6 tonnes  34 tonnes 0.5 tonnes  2.83 tonnes Higher Grade Chemistry

3. 170 230 percentage yield = x 100 = 73.9% Calculation of percentage yield. Calculations for you to try. 2. Ethene reacts with steam to ethanol C2H4 + H2O  C2H5OH Calculate the percentage yield of ethanol when 140g of ethene reacts to form 170 g of ethanol. C2H4 + H2O  C2H5OH 1 mol  1 mol 28 g  46 g 140 g  140/28 x 46 g  230 g Higher Grade Chemistry