# How do you find the rate of reaction given the rate constant and concentrations if you don’t have the time?

Aug 21, 2017

You don't need the time. We take by convention the reaction rate as the initial rate ${r}_{i} \left(t\right) \approx r \left(t\right)$, i.e. the rate at time zero,

overbrace(r(t))^("rate") = overbrace(k)^"rate constants"overbrace([A]^m[B]^n)^" concentrations",

(where $m$ and $n$ are reaction orders with respect to each reactant, and $k$ is the rate constant)

for the general reaction

${\nu}_{A} A + {\nu}_{B} B \to {\nu}_{C} C + {\nu}_{D} D$,

where $\nu$ is the stoichiometric coefficient, $A$ and $B$ are reactants, and $C$ and $D$ are products.

The rest of the process depends on the problem, but this is usually where you would start, as the reaction rate usually decreases over time.