Vitamin C - Iodide/iodate titration HD

Vitamin C will react with iodine in aqueous solution in a redox reaction. The vitamin C is oxidised to dehydroascorbic acid and the iodine molecules are reduced to iodide ions. Since iodine is relatively insoluble in water, it is generated in situ during this titration by the reaction of potassium iodate with potassium iodide. As long as vitamin C is present in the solution, the iodine, brown in colour, is converted to the iodide ion, colourless, very quickly. However, when the all the vitamin C is used up, the iodine present will react with starch to form a blue-black complex. The blue-black colour is the endpoint of the titration.