Atom Economy and Percentage Yield

  • Created by: India.02
  • Created on: 28-04-19 19:37
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  • Atom Economy and Percentage Yield
    • Atom Economy
      • % of  reactants forming useful products
      • 100% atom economy means that all atoms in the reactants have been turned into desired product - the higher the atom economy, the 'greener' the process
    • High and Low Atom Economy
      • Low atom economy means resources are used up very quickly and they make lots of waste materials that have to be disposed of - reactions tend to be unsustainable if the raw materials are non-renewable
        • Reactions may not be profitable because raw materials are expensive and waste can be expensive to dispose of responsibly
      • Find a use for the waste rather than throwing it away - come up with a reaction that gives useful by-products
      • Reactions with the highest atom economy usually only have one product - these have an atom economy of 100%
      • The more products there are, the lower the atom economy is likely to be
    • Percentage Yield
      • Compares actual yield and theoretical yield
      • Always between 0% and 100% - 0% yield means that no reactants were converted into product - 100% yield means you got all the product you expected to get
      • Industrial processes should have high percentage yield to reduce waste and costs
      • Yields will always be less than 100% because some reactant or product is always lost
      • Three common problems
        • Not all reactants react to make a product - in a reversible reaction the products can turn back into reactants - yield will never be 100%
        • There might be side reactions - reactants may react differently to how you expect - they might react with gases in air or impurities in the mixture
        • You lose product when you separate it from the reaction mixture - when you filter a liquid to remove solid particles you nearly always lose some liquid or solid


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