![[Reaction Rate - General Case]](../images/one1.gif) |
BASIC PRINCIPLES
Review
An Elementary Reaction is one which takes place in a single step on the molecular level.
Reaction Rates
There are several ways in which the rate of a reaction can be defined. In the simplest terms it can be defined as the rate of change of the concentration of a species participating in the reaction, be that species a reactant or product.
Taking the example A → B, the rate of the reaction is the change in concentration of A or B per unit time. Mathematically this is:
r = - d[A]/dt = + d[B]/dtNote the signs : -ve before a reactant and +ve before a product.
For the general case:
Note that the units of the rate of reaction are always mol dm-3 s-1.
Review Question
For the reaction NO + NO3 → 2NO2 , the rate of reaction can be expressed as
r = + d[NO]/dt = + d[NO3]/dt = - ½ d[NO2]/dtr = + d[NO]/dt = + d[NO3]/dt = - d[NO2]/dt
r = - d[NO]/dt = + d[NO3]/dt = + ½ d[NO2]/dt