Why is the yield in chemical reactions often less than 100%?

In chemical reactions, achieving a yield of 100% is often unrealistic due to several factors that can affect the amount of desired product formed. One significant reason is the occurrence of side reactions and losses.

Side reactions happen when reactants can form alternative products, leading to a reduction in the amount of the main product produced. Additionally, during the process of isolating and purifying the products, there can be losses due to mechanical handling, evaporation, or incomplete transfer of materials.

These factors collectively prevent the reaction from producing the maximum possible yield, thus resulting in an actual yield that is often lower than the theoretical yield calculated based on stoichiometric amounts of reactants. This understanding is crucial for chemists when they assess the efficiency of reactions in practical applications.