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Calculating percentage yield explained

Syllabus VWO: Quantities and relationships

Calculate percentage yield and assess whether a result is plausible.

A maximum and a measurement

The theoretical yield follows from the reaction ratio and limiting reactant. The actual yield is the amount of pure product obtained. Percentage yield = actual / theoretical × 100%.

More than 100% needs an explanation

A wet or impure product can give an excessive measured mass. This does not prove extra conversion. Percentage yield is also different from energy efficiency or atom economy.

Worked example

Theoretically 1.60 mol NH₃ forms. M = 17.0 g/mol. You collect 20.4 g.

  1. Theoretical mass = 1.60 × 17.0 = 27.2 g.
  2. Percentage yield = 20.4 / 27.2 × 100%.

The yield is 75.0%.