Useful Concepts

1. Ensure you have a correctly balanced equation for the reaction performed.
2. Determine how many moles of each species were used in the reaction.
3. Determine which species is the limiting reagent, remembering to use the reaction stoichiometry.
4. From the weight of product obtained, determine how many moles of product this corresponds to.
5. Taking into account the stoichiometry, determine what % this is compared to what you could have obtained by 100 * [moles product obtained]/[ maximum moles product possible]

For example: 8.21g of cyclohexene was reacted with 17.5g of bromine in chloroform, giving 20g of trans-1,2-dibromocyclohexane.

Stoichiometry of this reaction is 1:1
Moles of each species involved:
cyclohexene = 0.10 mol, Br₂= 0.11 mol, dibromocyclohexane = 0.083 mol.
Limiting reagent is therefore the cyclohexene.
Theoretical yield of dibromocyclohexane is 0.10 mol., therefore, experimental yield = 0.083./0.10 = 83 %

© Dr. Ian Hunt, Department of Chemistry