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Mark Roseman

Why is sulfuric acid used in a vitamin C (redox iodine) titration?

Ali Zaker Apurbo  Follow

Sulphuric acid is used in vitamin C determination to provide an acidic medium that will enable the liberation of iodine by the reaction of KI and KIO3.

The ionic equation is represented as follows;

I^- + IO3^- + 6H^+ ➡ I2 + 3H2O

I hope this helps.

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Dave McGlade  Follow

Well…. Let me brief this up…

Vitamin C reacts with I2 in redox manner, QUANTITATIVELY!

Here I2 is generated by mixing KI and KIO3

They react to produce I2 in ACIDIC MEDIUM only Hence H2SO4 is added!

5I- + IO3–+ 6H+ → 3I2 + 3H2O

This I2 solution is used for titration.

Normally ascorbic acid solution, mixed with strach solution drops titrated against this I2 solution!

When ascorbic acid is used up, blue colour persists to the addition of few further drops of I2 solution!- the end point!

Hope this helps!

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