Rate Of Reaction

A reaction is defined as a process in which a substance is converted into a new substance with changing their physical as well as chemical properties. And how fast a reactant converts to a product is nothing but the rate at which the reaction proceeds. 

Every chemical reaction proceeds at different reaction's rate. Some reaction occurs very fast like the combustion of match sticks, on the other hand, some reaction occurs very slow like rusting of iron in presence of air and moisture. So, we can say that different reactions take place at different speeds. To understand how the reaction is going to proceed, we determine the term "Rate Of The Reaction". 

Let us understand more about the rate of reaction. But before that you should be aware of one term, which is Rate Law. Let us now understand what it is?
An equation which shows a relationship between a 'Rate Of Reaction' and 'The Concentration Of It's Reactants' is called "Rate Law" for a reaction. 

Let's have a look a general chemical reaction,
              aA   +   bB     ➞     cC   +   dD
              Reactants                  Products 
Here, A and B are reactants and C and D are products. And a,b,c&d are the stoichiometric coefficients of the reactant and the product.
The rate law for this reaction can be written as;
           ➩ { r = k[A]ⁿ [B]ᵐ......... }
                            ------------------------(1)
 Where, 
             r     =  Represent the rate of reaction
     [A], [B]  =  Reactant's concentration 
             k     =  Represent reaction rate constant 
      " n+m"  =  Reaction order 
The rate constant of a reaction is equal to the rate of reaction when the concentration of each of the reactant is unity.
       
Rate Of Reaction
As per the general definition ,"The rate of chemical reaction is defined as a speed with which a reactant is converted into product or a speed at which a reaction takes place". In other words, a rate of reaction can be defined in terms of the amount of the reactants consumed or product formed in a unit of time.

Generally, when a reaction is takes place, then the concentration of reactant decreases with time while the concentration of the product increases with time and after the completion of the reaction, the whole reactant is converted into product. And how fast this reactant turns into a product can be detected by the rate of the reaction.

For more clarification, we can also define a rate of reaction into two ways;  
• The Rate At Which The Concentration Of The Reactant Decreases.
• The Rate At Which The Concentration Of The Product Increases.


☛ The rate of reaction is generally seen to be influenced by the composition of the reactant molecules and the energy of the reactant molecules (energy generally means temperature). Therefore we can say that, 
        ➩ -rA = fun{temperature, concentration}
☛ "The rate of a chemical reaction is the change in the concentrations of reactants or products in a given time interval".



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