Skip to main content
Examonaut
Sign in

GCSE Chemistry · AQA 8462 · Topic 4.3.3

Yield and atom economy of chemical reactions

Key points

  • The yield is the amount of product obtained. The theoretical yield is the maximum possible mass calculated from the equation.
  • percentage yield=mass of product actually mademaximum theoretical mass×100\text{percentage yield} = \frac{\text{mass of product actually made}}{\text{maximum theoretical mass}} \times 100
  • Yields are below 100% because the reaction may be reversible, some product is lost when separated from the mixture, and unexpected side reactions can occur.
  • Atom economy is the percentage of the reactant atoms that end up in the useful product: Mr of desired productsum of Mr of all reactants×100\frac{M_r \text{ of desired product}}{\text{sum of } M_r \text{ of all reactants}} \times 100 (using the balanced equation).
  • A high atom economy is better for sustainability and cost because less waste is produced.
  • Choosing a reaction pathway depends on atom economy, yield, rate, equilibrium position and the usefulness of any by-products.

Topic notesPremium

Reactions rarely give all the product the equation predicts, and many make products nobody wants. Percentage yield and atom economy measure how efficient a reaction is, which matters for cost and sustainability.

Unlock the full notes with Premium

Premium includes full topic notes, the paper generator, self-quizzes and progress tracking.

See Premium plansAlready Premium? Sign in

Practise this topicPremium

Premium members can generate an exam-style paper with a mark scheme, or take a quick quiz, on Yield and atom economy of chemical reactions.

Back to all Chemistry topics