What is the equivalent mass of O₂ in the following reaction?

${\mathrm{H}}_2\mathrm{O}+\frac{1}{2}{\mathrm{O}}_2+2{\mathrm{e}}^{-}⟶2{\mathrm{OH}}^{-}$

To determine the equivalent mass of oxygen (O₂) in the given reaction, let us understand the concept of equivalent mass:

Equivalent mass is calculated using the formula:

Equivalent mass = Molecular mass / Number of electrons involved per mole

Step-by-step Explanation:

1. From the reaction, it is evident that 1 mole of O₂ accepts 4 moles of electrons to participate in the formation of hydroxide ions (OH^-).
2. The molecular mass of O₂ is 32 g/mol (calculated as the sum of atomic masses of two oxygen atoms: 16 + 16).
3. Since the number of electrons involved per mole of O₂ is 4, the equivalent mass of O₂ can be calculated as:

Equivalent mass = Molecular mass / Number of electrons
Equivalent mass = 32 / 4 = 8

The equivalent mass of O₂ in the given reaction is 8 g/mol.

Concept Recap:

In redox reactions, the equivalent mass of a substance is determined by dividing its molecular mass by the number of electrons it accepts or donates per mole. In this reaction, oxygen (O₂) accepts 4 electrons per mole, making its equivalent mass one-fourth of its molecular mass.

Thus, the equivalent weight of oxygen is 8 g/mol.