1.1.17

Percentage Yield

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Percentage Yield

The percentage yield for any reaction is usually less than 100%. The following 5 factors cause deviations from 100%.

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Incomplete reactions

  • An incomplete reaction can happen because:
    • The reaction is very slow and hasn't been given enough time to happen.
  • The reaction is reversible and some of the products have turned back into reactants.
  • This reduces the percentage yield.
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Waste

  • Some of the chemicals will remain stuck to the glassware and will be wasted.
  • This reduces the percentage yield.
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Extraction

  • It might be difficult to fully separate the product from the reaction mixture.
  • This reduces the percentage yield.
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Side reactions

  • Unexpected reactions (side reactions) can happen. This may mean that the intended product is not created.
  • This reduces the percentage yield.
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Hydration

  • If a reaction is carried out in water, any extracted product may be 'wet'
  • This means that there is water in the extracted product.
    • Water is generally extremely difficult to fully remove from a product.
  • If a percentage yield is calculated to be over 100%, it is likely that your product is full of water.

Calculating Percentage Yield

The percentage yield of a reaction is calculated as the real yield divided by the theoretical yield multiplied by 100.

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Real yield

  • The real yield is the mass of the desired product obtained from a reaction.
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Theoretical yield

  • The theoretical yield is the maximum mass of a product that could possibly be created from a reaction.
  • This can be calculated from a balanced equation if we know the mass of the reactants.
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Percentage yield

  • A comparison of the real and theoretical yields of a reaction.

Jump to other topics

1Principles of Science I

1.1Structure & Bonding

1.2Properties of Substances

1.3Cell Structure & Function

1.4Cell Specialisation

1.5Tissue Structure & Function

1.6Working with Waves

1.7Waves in Communication

2Practical Scientific Procedures and Techniques

3Science Investigation Skills

4Principles of Science II

4.1Extracting Elements

4.2Relating Properties to use of Substances

4.3Organic Chemistry

4.4Energy Changes in Industry

4.5The Circulatory System

4.6Ventilation & Gas Exchange

4.7Urinary System

4.8Cell Transport

4.9Thermal Physics

4.10Materials

4.11Fluids

5Contemporary Issues in Science

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