# Equivalent Weight Calculation - Double Decomposition Method

Formula

EW2= (EW1*weight of CB/weight of AB)

A chemical reaction between two compounds in which the first and second parts of one reactant are united, respectively, with the second and first parts of the other reactant is termed as Double Decomposition method. This double decomposition method enables us to find the equivalent weight not only for the compounds but also for the component ions AB+CD--->AD+CB

Double Decomposition is also called as metathesis which is a chemical reaction between two compounds in which part of the first compound becomes united with part of the second.  In other words, the remainder of the first compound becomes united with the remainder of the second (as in AB + CD = AD + BC)

Example:
Calculate the equivalent weight of CB through double decomposition method.
Weight of AB = 25
Weight of CB = 30
Equivalent weight of AB(EW1) = 15

Solution:
Apply Formula:
EW2= (EW1*weight of CB/weight of AB)

Equivalent weight of CB (EW2) = 50