Answer to Question #98310 in General Chemistry for Mario

Question

Why do we add HCl to iodine in the titration of vitamin C?

Answer 1

ON adding hydrochloric acid to a solution of ascorbic acid, reversible oxidation with 2: 6-dichloro-phenolindophenol and iodine becomes progressively slower as the mineral acid content increases. When the hydrochloric acid concentration reaches 20 percent in the case of indophenol and 29 per cent in the case of iodine, reduction of the reagent is completely inhibited. On diluting the acid mixture with water, the total reducing capacity of the ascorbic acid is restored, and can be titrated with both reagents