The Rate of a Reaction: Chemistry 
The Rate of a Reaction The area of chemistry that deals with the rate or speed of chemical reactions is known a chemical kinetics. The word “kinetic” is derived from the Greek name kinitikos that means movement or motion. In the present context, the kinetic means the reaction rate or rate of a reaction that is defined as the change in concentration of a reactant or a product with time (M/s). Chemical reaction can be represented by the following general equation. Reactants Products
It is very important for you to understand the meaning of the above equation, which tells us that, during the course of a reaction, the reactant molecules are used up and product molecules are formed. The arrow between the reactants and products indicates the direction of the reaction. Let us represent reactant molecules by A and product molecules by B. Then we can re-write the above equation in the following from: A B (1)
This is a very simple reaction where A molecules are converted into B molecules or one mole of A disappears for each mole of B forms. As the time progresses, the number A molecules decrease and B molecules increase that is shown in the following figure.
100 80 No. of molecules B molecules 60 40 20 0 0 2 4 Time 6 8 10 A molecules
When we say “rate”, it usually means the change in some property with change in time. rate = change in roperty Δproperty = change in time Δtime
where the Greek symbol Δ ( pronounced as delta ) is used to mean “change”. Let us say that you have plant in your house that grew from 10 cm to 25 cm in two weeks (14 days). Then the rate of growth of a plant per day is, 1
rate of growth = (25 cm – 10 cm) / 14 day = 15 cm / 14 day = 1.07 cm/day Keep in mind that here the day is used for time. In addition, the calculated rate is the overall rate for the entire time period (14 day); it does not give you the growth by day. As far as chemical reactions are concerned, some property is the concentration and time is in seconds. Hence, the rate
It is very important for you to understand the meaning of the above equation, which tells us that, during the course of a reaction, the reactant molecules are used up and product molecules are formed. The arrow between the reactants and products indicates the direction of the reaction. Let us represent reactant molecules by A and product molecules by B. Then we can re-write the above equation in the following from: A B (1)
This is a very simple reaction where A molecules are converted into B molecules or one mole of A disappears for each mole of B forms. As the time progresses, the number A molecules decrease and B molecules increase that is shown in the following figure.
100 80 No. of molecules B molecules 60 40 20 0 0 2 4 Time 6 8 10 A molecules
When we say “rate”, it usually means the change in some property with change in time. rate = change in roperty Δproperty = change in time Δtime
where the Greek symbol Δ ( pronounced as delta ) is used to mean “change”. Let us say that you have plant in your house that grew from 10 cm to 25 cm in two weeks (14 days). Then the rate of growth of a plant per day is, 1
rate of growth = (25 cm – 10 cm) / 14 day = 15 cm / 14 day = 1.07 cm/day Keep in mind that here the day is used for time. In addition, the calculated rate is the overall rate for the entire time period (14 day); it does not give you the growth by day. As far as chemical reactions are concerned, some property is the concentration and time is in seconds. Hence, the rate