Second Order Reactions

Second-order reactions are chemical reactions that are dependent on the concentrations of either two first-order reactants or one second-order reactant.

Because second-order reactions can be any of the two types outlined above, their rates can be generalized as follows

r=k[A]x[B]y

Rate of Reaction :

Let a reaction be – aA + bB cC + dD 

In terms of reactant concentrations, the second-order reaction rate can be represented as r=k[A]x[B]y

[A] and [B] Reactant concentrations are constants in this case.

x and y are experimentally determined reaction orders, not the stoichiometric coefficients a and b.

The order of a chemical reaction is determined by the sum of the variables x and y. A second-order reaction is one in which x + y = 2. This can happen if one reactant is consumed at a rate proportional to its concentration squared (rate =k[A]2), or if both reactants are consumed at a rate proportional to their concentration squared (rate = k[A][B]). A second-order process’ rate constant, k, is measured in M-1s-1.

Few Examples :

N2Ois broken down into nitrogen monoxide and oxygen. The following is a response:

2N2O 2NO + O2

Hydrogen ions and hydroxyl ions make up water.

H+ +OH– H2O

In the presence of a base, hydrolysis of an ester occurs.

CH3COOC2H5 + NaOH CH3COONa + C2H5OH

Hydrogen Iodide is broken down into two gasses: hydrogen and iodine.

2HI → H2+ I2

Differential and Integrated Rate Equation for Second-Order Reactions

In the instance of a second order reactant generating a specific product in a chemical reaction, the differential rate law equation is as follows:

-d[A]/dt =k[A]2

To derive the integral rate equation, this differential form must be rearranged as follows.

-d[A]/[A]2= -kdt

Half Life of these Reactions :

A chemical reaction’s half-life is the time it takes for half of the initial amount of reactant to move through the reaction. As a result, while attempting to determine a reaction’s half life, the following substitutions must be made:

R = [R]O2

And

t = t12

When these values are substituted in the integral form of the rate equation for second order reactions, we get:

1[R]02–1[R]0= kt1/2

As a result, the half-life equation for second-order reactions can be expressed as follows.

t1/2= 1k[R]0 

Difference Between First and Second Order Reactions :

Graph Of Second Order Reaction :

Conclusion :

A second-order reaction is a type of chemical reaction in which the outcome is determined by the concentrations of one second-order reactant or two first-order reactants. In a second-order reaction, the total of the exponents in the rate law equals two.

r = k[A]x[B]y is the rate of second-order reactions.