Worked example

First order: rate=k[A].

Rate Law

Express rate dependence on concentrations with orders.

Equation

$\text{rate}=k[A]^m[B]^n$

Inline: $\text{rate}=k[A]^m[B]^n$$

Variables

Symbol	Quantity	Unit	Notes
$rate$	reaction rate	M·s⁻¹	—
$k$	rate constant	varies	—
$[A]$	concentration	M	—
$m,n$	orders	—	—

Conditions and limitations

Orders from experiment, not stoichiometry.

Rearrangements

$k=rate/([A]^m[B]^n)$

Dimensional check: M/s ✓

Worked example

First order: rate=k[A].

Steps: write equation → substitute with units → check dimensional consistency → report with correct significant figures.

Common errors

• Assuming orders equal coefficients

Related resources

• chemical-kinetics topic
• Calculators — linked only when a real calculator implements this formula.
• Constants — sourced constants with version when values are required.

Sources

• NIST Physical Constants 2022 — CODATA.

Reviewed 2026-08-21 by Editorial Team; due 2027-08-21.