Question

Explain the following terms:
(i) Rate constant $\left(k\right)$
(ii) Half life period of reaction $\left(t_{1/2}\right)$

Answer 1

(i) Rate constant (k):
The rate constant is the rate of the reaction if all the concentrations are set equally to unity. It is independent of concentration but depends on temperature.
The rate constant is proportionality constant and is also called specific reaction rate.
Thus for the reaction $A\to B$ , the rate law expression is $rate=k\left[A\right]$ and k is the rate constant.
(ii) Half-life period of reaction ($t_{1/2}$):
The half life period of a reaction is the time needed for the reactant concentration to fall to one half of its initial value.
For example, if the initial concentration of a reactant is 1 M and in 30 minutes, the concentration reduces to one half, i.e., it becomes 0.5 M, then the half life period is 30 minutes.