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Moles & Yield

Chemistry: AQA GCSE Higher, topic 3.1.19

Moles & Yield

You can calculate the number of moles of a compound or element if you have some other information about the quantities involved. You can then use this to calculate the percentage yield of a reaction.

Moles from concentration

Moles from concentration

  • You can calculate the number of moles in a solution by using the following equation:
  • Concentration = molesvolume\large\frac{moles}{volume}
  • This can be rearranged to:
  • Moles = concentration × volume
Moles from mass

Moles from mass

  • You can also calculate the number of moles of a substance by using the following equation:
  • Moles = massrelative  formula  mass\large\frac{mass}{relative \;formula\;mass}
Calculating theoretical yield

Calculating theoretical yield

  • You can use the number of moles and a balanced equation to calculate the theoretical yield.
  • This is the amount of product you'd expect to produce in a reaction if all the reactants were used up.
Calculating percentage yield

Calculating percentage yield

  • You can work out the percentage yield using the following equation:
  • Percentage yield = actual  yieldtheoretical  yield\large\frac{actual \;yield}{theoretical \;yield} × 100

Test yourself on Moles & Yield

  • Look at the following equation:
    2Fe + 3Cl2 → 2FeCl3
    If there is 0.54 moles of chlorine used in the reactants, how many moles of iron chloride are expected in the products?

  • Which is the correct equation for calculating the number of moles?

  • Which is the correct equation for calculating the number of moles using mass?

  • What does the theoretical yield of a reaction represent?

  • Which equation is used to calculate the percentage yield of a reaction?

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