The order of reaction with rate law expression, $\frac{d[R]}{dt} =-k$, is

0

The correct answer is Option (1) → 0

The order of a reaction is determined from the dependence of the rate of reaction on the concentration of reactants.

For a zero order reaction, the rate of reaction is independent of the concentration of the reactant. The rate law for a zero order reaction is: Rate = − d[R] / dt = k

This means the rate remains constant during the reaction, because it does not depend on the concentration of the reactant.

Thus, d[R] / dt = −k represents the rate law of a zero order reaction.

The integrated rate equation for a zero order reaction is: [R] = [R]₀ − kt where

[R]₀ = initial concentration  ; [R] = concentration at time t

Therefore, the reaction follows zero order kinetics.