How to Determine Order of Reaction
Identify the rate equation from the reaction., Identify the order of each reactant., Add the order for all reactants together.
Step-by-Step Guide
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Step 1: Identify the rate equation from the reaction.
Only 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., 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. , 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. -
Step 2: Identify the order of each reactant.
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Step 3: Add the order for all reactants together.
Detailed Guide
Only 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., 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. , 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.
About the Author
Charles Hughes
Specializes in breaking down complex practical skills topics into simple steps.
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