Question

Rate of reaction, $A+2B\to \text{Product}$ is$R=k{\left[B\right]}^2\left[A\right]$. If B is taken in large excess then the order of reaction is

• A. Pseudo second order
• B. Pseudo first order
• C. First order
• D. Second order

Answer 1

The correct option is B Pseudo first order

Pseudo order reaction:
A reaction whose order is different from the actual due to excess concentration of one of the reactants is called pseudo order reaction.

$A+2B\to P$
$Rate,R=k{\left[B\right]}^2\left[A\right]$
When B is taken in excess, then the reaction will be independent of [B] and is dependent on [A].

Here, the reactions is actually third order but behave as first order reactions. This reaction is called pseudo first order reaction.