If you were to perform this reaction in a lab, you would make far less than the theoretical yield of product due to a wide range of outside factors. We can compare the actual yield to the theoretical yield to calculate the percent yield:
percent yield=actual yieldtheoretical yield×100%

Keep in mind that the percent yield can be calculated using any unit of mass or moles, so long as they are the same. For example, you can divide moles by moles, or grams by grams, but you cannot divide moles by grams or vice versa.

What is the percent yield if the actual yield from this reaction is 166g?