When calculating percent yield, what must be determined first?

To calculate percent yield accurately, it is essential to determine the theoretical yield first. The theoretical yield represents the maximum amount of product that can be generated from a given amount of reactants, assuming complete conversion and perfect efficiency under ideal conditions. This value acts as a benchmark against which actual yield is compared.

Percent yield is calculated using the formula:

[ \text{Percent Yield} = \left( \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \right) \times 100 ]

Without knowing the theoretical yield, there would be no basis for evaluating the actual yield achieved in an experiment, preventing any meaningful assessment of efficiency. This foundational step is crucial in chemistry, especially when analyzing the effectiveness of reactions and processes involved in various scientific applications.