= Chemical yield
A <chemical yield> states how much specified material is obtained after a <chemical reaction> or separation, relative to an explicitly stated reference amount.<IUPAC Compendium of Chemical Terminology, fifth edition (Gold Book)>[Chemical yield, entry C01041]{ref} In synthetic chemistry, the reference is commonly the theoretical product amount allowed by the limiting reactant and <stoichiometry>:
$$
Y=\frac{n_{\rm obtained}}{n_{\rm theoretical}},\qquad \%Y=100Y.
$$
For $2A\to B$, starting with $0.10$ <mole> of $A$ permits at most $0.050$ <mole> of $B$. Isolating $0.040$ <mole> gives $80\%$ yield. An isolated yield includes workup losses; an assay yield measures product in a mixture. Neither is automatically the same as reactant conversion, and a reported yield needs a purity and measurement convention.
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