The percent yield of a chemical reaction is determined using the relationship between the actual yield and the theoretical yield.

Here's the formula:

Percent Yield = (Actual Yield / Theoretical Yield) x 100%

Let's break down each part:

* Actual Yield: This is the amount of product you actually obtain from the reaction. It's measured experimentally.

* Theoretical Yield: This is the maximum amount of product you could theoretically obtain based on the stoichiometry of the balanced chemical equation and the limiting reactant. It's calculated using the balanced chemical equation.

Example:

If you were to react 10 grams of reactant A with 20 grams of reactant B, and the theoretical yield calculated from the balanced equation is 15 grams of product C, but you only obtain 12 grams of product C after the reaction, then the percent yield would be:

Percent Yield = (12 grams / 15 grams) x 100% = 80%

This means you obtained 80% of the maximum possible amount of product C.