Question

If a reaction has an order of two, write two rate laws that could describe the reaction. Please explain in a well-developed paragraph.

Answer 1

For a second order reaction:   2A products

# The rate of reaction is directly proportional to the square of the concentration of one of the reactants.

Differential Rate Law:

r = k [A]²

The rate constant, k, has units of L mol^-1 sec^-1.

The integrated rate law :

1/[A] = kt + 1/[A_o] sinc At t = 0, the concentration of A is [A]₀.   

Concentration dependance of rate is called differential rate equation. It is not always convenient to determine the instantaneous rate , as it is measured by determination of slope of the tangent at point 't' in concentration vs time plot. This makes it difficult to determine the rate law and hence the order of the reaction. Inorder to avoid this difficulty, we can integrate the differential rate equation to give a relation between directly measured experimental data, i,e., concentrations at different times and rate constant.