Kelly Brechin

Vitamin C Stain Remover

SCIENCE CONCEPT: To see an oxidation/reduction reaction.

MATERIALS:

• Vitamin C tablets/Ascorbic Acid
• Iodine/Potassium Iodide Solution (you may be able to find tincture of iodine in the drug store
• Distilled water
• Bleach
• 1% starch solution (laundry starch will work)
• two - 400 mL beakers

DIRECTIONS:

1. Add 250-300 mL of distilled water into each beaker.

2.Put 2 mL of iodine solution into each of the beakers.

3. Add 2 mL of starch solution into only one of the beakers. The starch acts as a very specific indicator for the iodine in the element state.

4. Add a vitamin C tablet (ascorbic acid) to two beakers--one with pure iodine and one with the starch added. Gently swirl the beakers.

5. After 30-60 seconds, the color of the iodine solutions will begin to lighten and eventually fade completely.

6. Add 3 mL of bleach to all of the solutions. The yellow color returns and maybe the blue black colors returns and then disappears again.

INTRODUCTION:

How many of you spill food on your clothes when you eat? Well, I always do. In my demonstration today, I will mix chemicals to remove any stains.

EXPLANATION: The first reaction shows the difference in color properties of the iodine element (Yellow in water). Iodine is a diatomic element with the formula, I2. The starch reacts with the iodine element to form a blue -black color. Starch is a long polymer molecule in one shape of a coil - like the spring on a spiral notebook. The iodine molecules goes inside of the coil and this is what makes it turn blue.

The vitamin C chemical gives an electron to each of the iodine atoms to form the iodide ion with a negative charge. This then shows that the iodide ion is colorless in water solution even in the presence of the starch. This reaction changes the form of the iodine element to the iodide ions.

The bleach, which contains sodium hypochlorite, removes the electrons from the iodide ion to reform the iodine element and shows the colors of the iodine element again, even if quite briefly. In the meantime, the Vitamin C is still reactive in giving electrons back to the iodine to make the colorless iodide ions.

The bleach removes the electrons from the ion form of iodine and the vitamin C gives electrons to the element from of the iodine.

Starch + I₂ = blue/black

I₂ + ascorbic acid --> 2 I^- (yellow) to (colorless)

Starch + I^- = colorless (ion form)

NaClO + 2 I^- --> I₂ (Yellow) (element form)

SAFETY: Exercise proper precautions when handling the chemicals. Both bleach and iodine may stain your clothes.

DISPOSAL: All chemicals may be disposed down the drain.

REFERENCE: Unknown