BACKGROUND RESEARCH

The pH scale is used to measure how acidic/ basic a solution is. Any pH lower than seven would be acidic and anything more is basic, on a scale from zero to fourteen. Seven, because it is half of fourteen, is neutral in pH. The solutions turn different colors depending on the level of acidity.

The pH indicator is a chemical used to see the level of acidity. The 3 indicators used in this project are: phenolphthalein, p-nitrophenol, and thymolphthalein. One of the solutions in the beaker would change color, when phenolphthalein is added, if it is a basic solution. The color change would be a light red as soon as the colorless solution and phenolphthalein are mixed together. P-nitrophenol starts off colorless, but when added to a base turns yellow and Thymolphthalein changes into blue when in a base.

There are six colorless solutions in six containers and only three pH indicators, so when you add two indicators to one solution it could change into a color other than red, blue, or yellow(primary colors). For example, when you mix red paint and yellow paint you get orange, when you mix red and blue it becomes purple, and so on. The pigments can be used to indicate pH level.

To get red you'd just add phenolphthalein to a solution that is higher than seven or basic. Thymolphthalein(blue) and phenolphthalein(red) together in a solution would make the color turn purple. P-nitrophenol(yellow) and thymolphthalein(blue) make green. Phenolphthalein and p-nitrophenol make orange. That is how you get the colors of the rainbow, R.O.Y.G.B.V., (Red, Orange, Yellow, Green, Blue, and Violet or Purple) in the six solutions.

Phenolphthalein- formula is C2OH14O4 (2 Carbon, 1 Oxygen, 14 Hydrogen, and 4 Oxygen) Colorless liquid, turns red when added to a basic solution.

Thymolphthalein- formula is C28H30O4 (28 Carbon, 30 Hydrogen, and 4 Oxygen) Colorless liquid, turns blue when added to a base.

P-nitrophenol-formula is C6H5NO3 (6 Carbon, 5 Hydrogen, 1 Nitrogen, and 3 Oxygen) Colorless liquid, turns yellow when added to basic solution.

Two solutions used as the base are: Sodium Hydroxide, and Hydrochloric Acid. After adding the pH indicators to the bases to make the color "dissappear" add alcohol to dissolve it and the indicator powder will settle at the bottom of the container.

Research/References

Porcja, Bob. "Rainbow Connection: Rainbow Colors with Mixed Acid-Base Indicators."

Rutgers. The Rutgers Chemistry Lecture Demonstration Facility, 14 Aug. 2012. Web.

5 Feb. 2014.

Helmenstine, Anne M. "Red Cabbage PH Indicator." About.com Chemistry. About.com,

2014. Web. 02 Feb. 2014.

Walke, Cynthia. "PH Scale." EPA. Environmental Protection Agency, n.d. Web. 05 Feb.

2014.

Askew, Jim. "Acids and Bases." Acids and Bases. The Internet Science Room, n.d. Web.

05 Feb. 2014.

"Hydrochloric Acid (Hydrogen Chloride)." EPA. Environmental Protection Agency, n.d. Web.

05 Feb. 2014. <http://www.epa.gov/ttnatw01/hlthef/hydrochl.html>.