Question

Describe Ostwald‘s isolation method for determination of order of reaction.Answer it in detail.

Answer 1

 

Methods of Finding the Order of Reaction

Ostwald Isolation Method

 

This method is introduced by Ostwald and is used to determine theorder of a reaction with respect to one reactant at a time. The totalorder of the reaction can be calculated by adding all the orders of thereaction for individual reactant.The principle behind this method is that if the concentration of all butone reactant is taken in excess, then during the course of reaction, theconcentration of those reactants taken in excess will remain constantand the variation in the rate will correspond to the concentration ofthat reactant whose concentration is small.The process is repeated for other reactants present in the chemicalreaction one by one and order with respect to each reactant can bedetermined. By adding all the orders of the individual reactant wewill get overall order of the reaction .For example,Suppose, we isolate A by taking B and in large excess and get orderof reaction with respect to A (say p) Similarly, q and r are the order ofreactions for B and C by taking C and A in excess for q order of B andA, B in excess for r order of C.



Answer 2

Answer:

In Ostwald isolation method, the concentration of all the reactant molecules is taken in excess except one.

Explanation:

The sum of the reaction orders for each individual reactant is then the reaction's overall order. This approach is based on the idea that, if all but one reactant is taken in excess, the concentration of those reactants will stay almost constant during the reaction and, as a result, rate variation will correspond to the concentration of that reactant whose concentration is tiny. The order with respect to each reactant is established by repeating this method one at a time.

The total of these orders will represent the overall order.

$aA+bB+\rightarrow Products$

The reaction is first carried out with B present in great excess. So the reaction must only depend on the concentration of A:

$r=k[A]^x$

Similarly, when the reaction is now carried out in a large excess of A, the rate of reaction must only depend on the concentration of B:

$r=j[B]^y$

The order, n, of the overall reaction is therefore:

$n=x+y$

#SPJ2