Question

How to identify zero oder, first, second order and third order reactions?

Answer 1

1
Identify the rate equation from the reaction. The rate equation can help you determine the order of the reaction. This equation shows the increase or decrease of a particular substance with respect to time. Other equations related to the chemical reaction will not help you identify the order of the reaction

2
Identify the order of each reactant.Each reactant listed in the rate equation will have an exponent of either 0, 1, or 2 (above 2 is very rare). That exponent denotes the order of that reactant. Looking at each exponent:

• A zero means that the concentration for that reactant has no bearing on the rate of reaction.
• A one means that increasing the concentration of this reactant will increase the rate of the reaction in a linear way (doubling the reactant doubles the rate).
• A two means that the rate of the reaction will increase by the square of the increased concentration (doubling the reactant will increase the rate by four times).
• Zero order reactants are often not listed in the rate equation, since any number to the zeroth power is equal to one.

3
Add the order for all reactants together. The overall order of a reaction is the sum of each reactants’ orders. Add the exponents of each reactant to find the overall reaction order. This number is usually less than or equal to two.

• For example, if reactant one is first order (an exponent of 1) and reactant two is first order (an exponent of 1) then the overall reaction would be a second order reaction.