(A) Rate constant : The rate constant of a chemical reaction is defined as the rate of the chemical reaction when the concentration (or active masses) of each reactant has unit value, i.e., 1 mol dm-3 in the case of solution and the pressure is 1 atm in case of gases, e.g., for a reaction,
A → products, Rate R = k[A].
If [A] = 1 mol dm-3, then k = R.
(B) The rate constant of a reaction depends on the following factors :
- Nature of the reactants.
- Temperature of the reaction. As the temperature increases, the velocity constant (rate constant) increases.
- The conditions of the reactions like the presence of the catalyst, solvent, pH, etc.
- It does not depend on the concentration of the reactants. But if one or more substances are in excess concentration, then the order of the reaction is independent of them.
