= Rate law
A <rate law> specifies how a <reaction rate> depends on <concentrations> under stated conditions. A common form is
$$
v=k[\mathrm A]^\alpha[\mathrm B]^\beta,
$$
where $k$ is a <rate constant> and the exponents are partial <orders of reaction>. Determine them experimentally, or derive them from a justified <reaction mechanism>. Do not infer $\alpha=a$ and $\beta=b$ from the net <chemical equation>: its coefficients describe consumption ratios, whereas the exponents describe sensitivity to <concentration>. See https://goldbook.iupac.org/terms/view/R05141[IUPAC Gold Book: rate law] and https://openstax.org/books/chemistry-2e/pages/12-3-rate-laws[Flowers et al., Chemistry 2e, §12.3: rate laws].
A <rate law> becomes a prediction of time evolution when combined with <stoichiometry> in a <rate equation>, for example $d[\mathrm A]/dt=-av$. Agreement with a measured <rate law> is useful evidence for a <reaction mechanism>, but several routes can give the same dependence.
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