Solution
Let R be the rate of reaction.
For first order reaction,
R=K[A]
1
⇒K=R[A]
−1
Whereas, K and [A] are rate constant and initial concentration of reactant respectively.
Therefore,
Unit of rate constant =(molL
−1
)
1−n
sec
−1
For first order reaction,
n=1
Unit of rate constant =sec
−1
Hence the unit of rate constant for first order reaction is sec
−1
.