chapter 6. CHEMICAL KINETICS class 12 chemistry textbook solution
3. Answer the following in brief.
xiii. What is zeroth order reaction? Derive its integrated rate law. What are the units of rate constant?
Answer:- Reactions in which the rate is independent of the reactant concentration are zeroth-order reaction.
The integrated rate law for zero-order reactions:
For a zero-order reaction, A → P, the differential rate law is given by:
rate = \(-\frac{d[A]}{[A]} = k[A]_0 = k \quad \text{(1)}\)
Rearranging Equation (1) gives:
\(d[A] = -k dt \quad (\because [A]^0 = 1)\)
Integration between the limits:
\([A] = [A]_0\) at \(t = 0\) and \([A] = [A]_t\) at \(t = t\) gives:
\(\int_{[A]_0}^{[A]_t} d[A] = -k \int_{0}^{t} dt\)
\([A]_t - [A]_0 = -kt\)
Hence, \(kt = [A]_0 - [A]_t \quad (2)\)
The unit of the rate constant for the zero-order reaction is mol dm-3 s-1.