| Rate constant of a reaction | Rate of a reaction |
| (i) It is constant proportionality in the rate law expression. | (i) It is the speed of which the reactants are converted into products at any moment of time. |
| (ii) It is constant and does not depend on the progress of the reaction. | (ii) It decreases with the progress of reaction generally. |
| (iii) It refers to the rate of the reaction at the specific point when concentration of every reacting is unity. | (iii) It depends upon the concentration of reactant species at that moment of time. |
| (iv) It has different units for different reactions. | (iv) It has same units for all reactions/mole sec |