Question

Why rate of reaction does not remain constant throughout?

Answer 1

Physical condition matters a lot

Answer 2

The rate of the reaction always depends upon the concentration of reactants/products per unit time.

That is, the rate of reaction = Decrease in concentration Of reactants per unit time

or

Increase in concentration Of products per unit time

Factors that affect the rate of a reaction are ;

           1. Nature of reactants

           2. Concentration of reactants

           3. The surface area of the reactants

           4. Temperature

           5. Catalyst and

           6. Light