Browse Questions

# What is the unit of k of a $n^{th}$ order reaction?

$\begin{array}{1 1} M^{\large\frac{1-n}{n}} s^{âˆ’1} \\ M^{n-1} s^{âˆ’1} \\ M s^{âˆ’1} \\ M^{1-n} s^{âˆ’1} \end{array}$

Answer: M$^{1-n}$ s$^{−1}$
The units of the rate constant depend on the global order of reaction: If concentration is measured in units of mol·L$^{−1}$ (sometimes abbreviated as M), then:
For order one, the rate coefficient has units of s$^{−1}$, which can be written as M$^{1-1}$ s$^{−1}$
For order two, the rate coefficient has units of M$^{-1}$s$^{−1}$, which can be written as M$^{1-2}$ s$^{−1}$
For order three, the rate coefficient has units of M$^{-2}$s$^{−1}$, which can be written as M$^{1-3}$ s$^{−1}$
Generalising for order n, the rate coefficient will have units of M$^{1-n}$ s$^{−1}$
edited Jul 26, 2014