Actual Yield Definition (Chemistry)

Actual Yield Definition

The actual yield is the quantity of a product that is obtained from a chemical reaction. In contrast, the calculated or theoretical yield is the amount of product that could be obtained from a reaction if all of the reactant converts to product. Theoretical yield is based on the limiting reactant.

Common Misspelling: actual yeild

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Theoretical Yield Definition in Chemistry

By Anne Marie Helmenstine, Ph.D.

Why Is Actual Yield Different from Theoretical Yield?

Usually, the actual yield is lower than the theoretical yield because few reactions truly proceed to completion (i.e., aren't 100% efficient) or because not all of the product in a reaction is recovered. For example, if you are recovering a product that is a precipitate, you may lose some product if it doesn't completely fall out of solution. If you filter the solution through filter paper, some product may remain on the filter or make its way through the mesh and wash away. If you rinse the product, a small amount of it may be lost from dissolving in the solvent, even if the product is insoluble in that solvent.

It's also possible for the actual yield to be more than the theoretical yield. This tends to occur most often if solvent is still present in the product (incomplete drying), from error weighing the product, or perhaps because an unaccounted substance in the reaction acted as a catalyst or also led to product formation. Another reason for higher yield is that the product is impure, due to the presence of another substance besides the solvent.

Actual Yield and Percent Yield

The relationship between actual yield and theoretical yield is used to calculate percent yield:

percent yields = actual yield / theoretical yield x 100%