Introduction
The conversion of iodate ions (IO₄⁻) to iodine (I₂) in acidic medium involves a redox reaction. Understanding the equivalent mass of IO₄⁻ in this context is crucial for stoichiometric calculations.

Redox Reaction
- In acidic medium, IO₄⁻ gets reduced to I₂.
- The balanced chemical equation for this reaction is:
\[ 2 IO_{4}^{-} + 10 H^{+} + 8 e^{-} \rightarrow I_{2} + 4 H_{2}O \]

Determining Equivalent Mass
- The equivalent mass of a substance in a redox reaction is calculated using the formula:
\[ \text{Equivalent Mass} = \frac{\text{Molar Mass}}{n} \]
where \( n \) is the number of electrons transferred per mole of substance.
- **Molar Mass of IO₄⁻:**
- Iodine (I): 126.9 g/mol
- Oxygen (O): 16 g/mol
- Total for IO₄⁻ = 126.9 + (4 × 16) = 126.9 + 64 = 190.9 g/mol
- **Number of Electrons Transferred (n):**
- From the balanced equation, 2 moles of IO₄⁻ transfer 8 electrons.
- Thus, for 1 mole of IO₄⁻, \( n = \frac{8}{2} = 4 \).

Calculating Equivalent Mass
- Substitute the values into the formula:
\[ \text{Equivalent Mass} = \frac{190.9 \text{ g/mol}}{4} = 47.725 \text{ g/equiv} \]

Conclusion
- The equivalent mass of IO₄⁻ when converted to I₂ in acidic medium is approximately **47.73 g/equiv**. This value is essential for titration and analytical chemistry involving iodate ions.