This section covers the distinction between the maximum calculated yield and the amount of product actually obtained.
Expected and experimental product
Theoretical yield
The theoretical yield is the maximum quantity of product predicted by a stoichiometric calculation from the amount of reactant available.
It may be expressed as a mass or as an amount in moles.
Actual yield
The actual yield is the quantity of product obtained experimentally.
It can also be recorded as a mass or an amount in moles.
Why actual yield can be lower
In practice, the amount of product collected can be below the calculated maximum because:
other reactions occur alongside the intended reaction;
the intended reaction does not proceed to completion;
some reactant or product is lost from the reaction system.
The theoretical yield is therefore obtained from the balanced equation and mole calculation, whereas the actual yield comes from the experimental result.