Q: Why are actual yields generally less than theoretical yields?

Flexi Says: The actual yield is generally less than the theoretical yield. This is due to fact that theoretical yield is the maximum possible yield predicted when the reaction happens perfectly without any waste of reactants. This is rare in practical conditions. In the course of an experiment, many things will contribute to the formation of less product than would be predicted. Besides spills and other experimental errors, there can be losses due to an incomplete reaction or undesirable side reactions.