TESTING FOR VITAMIN C

WHAT IS VITAMIN C? Essential nutrient for humans Healthy immune system Antioxidant Wound healing Water soluble: needs to be replenished daily

GOALTo determine the amount of Vitamin C in

different foods

Recommended Daily Intake Boys 14–18 years 75 mg Girls 14–18 years 65 mg

EXPERIMENT Titration is used to determine the

concentration of an unknown solution We will be using titration to determine the

amount of vitamin C in various foods

How is a titration performed?

TITRATION

Juice containing Vitamin C

Starch solution used as indicator

TITRATION Add iodine solution

drop by drop into the flask containing the juice/starch solution

When the solution changes color, stop adding iodine

Determine the volume of iodine used for the titration

Burette filled with iodine solution

Indicates presence of iodine

No Vitamin C left

Amount of iodine solution needed to titrate the Vitamin CStarch

Indicator turns purple/black

REACTION C6H8O6 + I3- + H2O C6H6O6 + 3I- + 2H+

In the presence of Vitamin C (C6H8O6), the iodide ion (I-) is produced

Iodide does not react with starch no color change

When there is no more Vitamin C left, the iodine will no longer react to produce iodide

The solution will turn purple, indicating the presence of iodine

Vitamin C colorless

No change in solution color: Vitamin C is present

Purple/Black solution: All Vitamin C has reacted

We will begin the experiment with a known concentration of Vitamin C to standardize our measurements

For example, 10ml of iodine solution was used to titrate the standard vitamin C solution with 0.25g of Vitamin C

Once we know how much iodine solution it takes to titrate our known concentration of Vitamin C,

We can experiment with other foods to find out how much vitamin C they have

10ml of Iodine solution

0.25g Vitamin C= 6ml of Iodine solution

? g Vitamin C

VS.

The more iodine solution needed for the titration, the more Vitamin C is contained in the food

We can use this to estimate how much Vitamin C we are getting in our diet and if we are meeting the nutritional recommendations!

QUESTIONS Why are we performing a titration? Why do we need vitamin C daily? What foods could we test for vitamin C

in our experiment? Do you think that you are getting

enough vitamin C in your diet? Why? What are the side effects of having an

insufficient amount of vitamin C in a diet?