Why is the actual yield of a reaction often not equal to the theoretical yield?

In chemistry, yield is a measure of the quantity of product formed in a chemical reaction. Theoretical yield is the maximum amount of product that can be formed from a given amount of reactants, as predicted by the stoichiometry of the balanced chemical equation. The actual yield, on the other hand, is the amount of product that is actually obtained from the reaction in a real-life experimental scenario.

There are several factors that can cause the actual yield of a reaction to be different from the theoretical yield. These factors include: 1. Reversible reactions: Some reactions are reversible, meaning they can proceed in both the forward and reverse directions. In such cases, the reaction may not go to completion, and the equilibrium position might not favor the formation of products to the extent predicted by the balanced chemical equation. 2. Side reactions: In many cases, the reactants can undergo other reactions besides the main reaction of interest, leading to the formation of unwanted side products. This can reduce the amount of reactants available for the main reaction, which results in a smaller actual yield of the desired product. 3. Loss of product during purification or isolation: When the products of a reaction are isolated and purified, some of the product may be lost due to factors such as transfer loss, filtration loss, and evaporation. This can result in a lower actual yield than theoretically predicted. 4. Limiting reagent: Often, one of the reactants is not present in stoichiometric amounts, meaning there is not enough of it to react with all the other reactants. This limiting reagent determines the maximum amount of product that can be formed, which can be less than the theoretical yield based on the initial quantities of all reactants.

The actual yield of a reaction is often not equal to the theoretical yield due to factors such as reversible reactions, side reactions, loss of product during purification, and limiting reagents. These factors can result in the formation of a smaller amount of the desired product than what is predicted by the stoichiometry of the balanced chemical equation.