Updated: Dec 7, 2020
Percentage yield is a sub chapter of chemical calculations. This article is meant to clarify this concept so that students will have no problems answering questions from this sub-chapter. In an experiment, 23g of Na reacted with excess hydrochloric acid producing 20 dm3 of hydrogen gas at room temperature and pressure. The reaction is as below, Na + 2HCl --> NaCl + H2 Molar mass of Na is 23g Mole of sodium present = 23/23 = 1 mol From the equation, 1 mol of sodium will produce 1 mol of hydrogen gas. At room temperature and pressure, 1 mol of hydrogen gas will occupy a volume of 24 dm3. However, in the experiment only 20 dm3 of hydrogen gas was collected , this means that the experiment did not produce 100% of the amount of hydrogen that we are expecting to get, in fact we are only getting 83% (20/24 x 100) of the expected amount , so the percentage yield is 83%. So percentage yield = Actual Yield/Theoretical Yield x 100 Summary: To find out the percentage yield, we need to (1): Use the chemical equation to determine the theoretical amount of product (theorectical yield) obtained for the amount of reactant. (2): Then we can used the given yield provided by the question to determine the percentage yield. A high percentage yield implies that we are getting the maximum amount of product we can get for the amount of reactant.