# What Is a Pseudo Order Reaction?

**A pseudo order reaction is a reaction that appears to be of a different order than it actually is, explains Datasegment.com.** For example, a pseudo first order reaction is a chemical reaction between two reactants, and is thus a second order reaction, which appears to be a first order reaction because one of the reactants is in such small quantity that it is not easily noticed.

A first order reaction is a mathematical concept that expresses decay at an exponential rate. The concept is applied to various rates of decay and is expressed in a differential equation. This equation is used to calculate the rates of decay for radioactivity and chemical reactions. Different variables can be plugged into the equation to determine various rates of decay. In the order reaction differential equation, the amount of decaying material is proportionate to the amount of remaining material. The equation is expressed as: dA/dt = -kt. The da/dt represents the rate of unit time that this quantity is increasing, while A = increase, t = time and k is a constant. A pseudo first order reaction is created using this equation when two reactants are entered, but one is substantially more dilute than the other.