Percentage Yield, Atom Economy + Uncertainty

Percentage yield formula

Actual Yield / Theoretical Yield * 100

Theoretical Yield

• Maximum amount of product that could be obtained in a reaction (usually calculate with a moles calculation)

Actual Yield

• The actual amount of a product obtained in a reaction

Percentage yield may be less than 100% because:

• Reaction is reversible

• Some products may be lost when separating from the reaction mixture

• Some reactants may undergo unwanted side reactions (incomplete combustion)

Atom economy formula

Total Mr of desired products / Total Mr of reactants * 100

Atom economy

• Measures the amount of reactants that end up as useful products

Higher atom economy is desired for:

• Sustainable developments

• Reducing waste (economic + environmental)

Experimental Uncertainty

• When taking a measurement with apparatus in a practical, there is some uncertainty in the reading

• From a set of results

• Identify + ignore anomalies

• Take mean of remaining results

• Form uncertainty

Uncertainty formula

uncertainty = +- range / 2

Concentration is measured in

g/dm cubed or mol / dm cubed

1 dm cubed

1000 cm cubed

moles (dm3)

concentration x volume (dm cubed)

moles (cm3)

concentration x volume (cm3 cubed) / 1000