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Summary AS Chemistry - 3.1.2 Amount of Substance: Percentage Yield and Atom Economy
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Detailed Notes for 3.1.2 Percentage Yield and Atom Economy :)
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Percentage Yield & Atom EconomyPercentage Yield:
Percentage yield tells you how wasteful a process is.
The equation for percentage yield is as follows:
Percentage Yield = (actual yield/theoretical yield) x 100
Percentage yield is never 100%.
Reasons for this include:
- Some may be lost in isolation (e.g. filter paper)
- Some may be lost in transfer
- Some of the reactants may not have reacted
- The reaction could be reversible
- Side reactions may be occurring at the same time
Atom Economy:
Atom economy tells you how wasteful a reaction is.
i.e. the proportion of reactants that become part of the desired product.
The equation for atom economy is as follows:
Atom Economy = (molecular mass of desired product/sum of molecular mass of reactants) x 100
A greater atom economy is desired because:
- There is less waste (easier to dispose & better for environment)
- More sustainable (since it’s a more efficient use of reactants)
- Easier and cheaper to separate the desired & waste products
When calculating atom economy, the numbers in front of the molecules in the equation
should be accounted for:
E.g. CH4(g) + H2O(g) → 3H2(g) + CO(g)
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