Reaction Rate
The change in concentration of a reactant or product per unit time.
Formula / equation
rate = −Δ[A]/(aΔt) = Δ[P]/(pΔt)
Unit
mol/(L·s)
In depth
Dividing each concentration change by the corresponding stoichiometric coefficient gives a single rate that is the same whichever species is monitored. Rates are always quoted as positive, so a minus sign is applied to reactant terms. Almost all reactions slow as reactants are consumed.
Examples in the real world
Monitoring a reaction by the volume of gas evolved per minute, or by the fading colour of a coloured reactant.