Equivalent weight is the quantity of a substance in chemistry that exactly reacts with, or is equal to the combining value of  a fixed quantity of another substance in a particular reaction. For an element the equivalent weight is the quantity that will combine with or replace 1.00797 grams (g) of hydrogen or 7.9997 g of oxygen; or, the weight of an element that is liberated in an electrolysis reaction by the passage of 96,500 coulombs of electricity. The equivalent weight of an element is given by its gram atomic weight divided by its valence. The link provides the formula to calculate the equivalent weight of a substance.

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