Question

Why the equivalent weight of oxygen is used here?

Answer 1

Answer:

In other words, the equivalent weight relates to a specific reaction - and by the way, its possible that the exact same two reactants can have different equivalent weights if they can combine in more than one stoichiometry.

Explanation:

Hope this helps you mate xD

Answer 2

Explanation:

Equivalent weight, in chemistry, the quantity of a substance that exactly reacts with, or is equal to the combining value of, an arbitrarily fixed quantity of another substance in a particular reaction.