With the help of a graphical representation explain how the rate of a first order reaction varies with the initial concentration of reactant.

Explanation

The rate of a first order reaction at any instant during the reaction is proportional to the concentration of the reactant at that instant.
That is, rate `prop` [reactant]or, rate = k[reactant] Thus, the rate of the reaction varies linearly with the concentration of reactant. The above reaction between the rate and the concentration of the reactant has the same form as an equation of a straight line of type y=mx .
Hence , plotting rate vs concentration of reactant , corresponding to various instants of time will give a straight line passing through the origin.