Consecutive or Sequential Reactions

This reaction is defined as that reaction which proceeds from reactants to final products through one or more intermediate stages. The overall reaction is a result of several successive or consecutive steps.

A → B → C and so on

Example of Sequential Reactions

·         Decomposition of ethylene oxide(CH2)2O  CH3CHOCH3CHO  CO + CH4·         The pyrolysis of acetone(CH3)2CO  CH4 + CH2 =C=O                                  CH2 =C=O  C2H4 + CO

For the reaction

…….(i)

………(ii)

……….(iii)

Integrating equation (i), we get

Now we shall integrate equation (ii) and find the concentration of B related to time t.

Integration of the above equation is not possible as we are not able to separate the two variables, [B] and t. Therefore we multiply equation (4) by an integrating factor , on both the sides of the equation.

Integrating with in the limits 0 to t.

Now in order to find [C], substitute equation (vi) in equation (iii), we get 

B_max and t_max:     

We can also attempt to find the time when [B] becomes maximum. For this we differentiate equation (vi)  and   find d[B]/dt & equate it to zero.

Substituting  equation (vii)  in equation (vi)