Question

What is Pseudo first order reaction? Derive integrated rate law equation for zero order reaction.

Hint:

For zero-order reactions, the concentration decreases linearly with time, and the slope of the concentration vs. time graph is equal to \(-k\).

Answer 1

Pseudo First-Order Reaction:
A reaction that is not actually first-order but behaves as if it were first-order is called a pseudo-first-order reaction. This typically occurs when one of the reactants is in excess and its concentration remains almost constant during the reaction, making the reaction rate depend only on the concentration of the limiting reactant. For example, the hydrolysis of an ester in water is a second-order reaction overall but is often treated as a pseudo-first-order reaction if the concentration of water is in large excess. Step 1: Zero Order Integrated Rate Law.
For a zero-order reaction, the rate law is given by: \[ \text{Rate} = k \] Where \( k \) is the rate constant. The integrated rate law for a zero-order reaction is derived from the equation: \[ \frac{d[A]}{dt} = -k \] Integrating with respect to time: \[ \int_{[A]_0}^{[A]} d[A] = -k \int_0^t dt \] \[ [A] - [A]_0 = -kt \] \[ [A] = [A]_0 - kt \] This is the integrated rate law for a zero-order reaction.