A second-order reaction is a type of chemical reaction that depends on the concentration of two first-order reactants or one second-order reactant. This reaction proceeds at a rate proportional to the product of the concentrations of two reactants and to the square of the concentration of one reactant.
In a second-order reaction, the sum of the exponents in the rate law is equal to two, that is why it is known as the second-order reaction. In many biological reactions, just like the formation of double-stranded DNA from the two complementary strands, this whole process is described by the kinetics known as the second-order kinetics.
There are two most common types of second-order reactions will be described in this section.