Percentage yield (Edexcel GCSE Chemistry): Revision Notes
📚 Revision Notes
3.3.1 Percentage Yield
What is "Percentage Yield?
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Percentage yield tells us how much of the reactants have been successfully turned into products in a chemical reaction. It compares what you actually get (the actual yield) to the maximum amount you could have gotten (the theoretical yield).
Why Don't We Always Get 100% Yield?
- In theory, if you start with 10 grammes of reactants, you should get 10 grammes of product. But in real life, this almost never happens because:
- Some reactions are reversible, meaning they don't go all the way to completion.
- Some product might be lost during separation from the reaction mixture.
- Some reactants might react in unexpected ways (e.g., reacting with oxygen in the air instead of with other reactants).
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How to Calculate Percentage Yield:
- The formula for percentage yield is:
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Example:
- Imagine you perform an experiment and produce 6.25 g of magnesium sulphate, but the maximum amount you could theoretically get is 8.5 g.
- Using the formula:
- So, in this example, your percentage yield is 73.5%, meaning you successfully converted 73.5% of the reactants into the product.