What is percentage yield in a chemical reaction?

Percentage yield in a chemical reaction is the ratio of the actual yield to the theoretical yield, expressed as a percentage.

In more detail, the percentage yield is a measure of the efficiency of a chemical reaction. It compares the amount of product that was actually produced (the actual yield) to the amount that could have been produced under perfect conditions (the theoretical yield). This is usually expressed as a percentage, hence the term 'percentage yield'.

The formula to calculate percentage yield is: (actual yield / theoretical yield) x 100%. For example, if a reaction has a theoretical yield of 10 grams but only 8 grams are actually produced, the percentage yield would be (8/10) x 100% = 80%.

Theoretical yield is calculated based on the balanced chemical equation for the reaction. It assumes that the reaction goes to completion with no side reactions or losses. However, in reality, reactions often do not go to completion, there may be side reactions, and some product may be lost during the purification process. Therefore, the actual yield is often less than the theoretical yield, and the percentage yield is less than 100%.

Understanding percentage yield is important in both academic and industrial chemistry. In the classroom, it helps students understand the efficiency of reactions and the factors that can affect this. In industry, it is crucial for cost-effectiveness and sustainability, as reactions with low percentage yields may waste resources and produce unwanted by-products. Therefore, chemists often aim to maximise the percentage yield of reactions.