(CHO) Power of Hydrogen Lesson

Power of Hydrogen 

pH is known as the degree of acidity or alkalinity of a liquid based on hydrogen ion concentration. The pH of a substance is measured on a scale from 0 to 14. This scale is called the pH scale. When water disassociates, it forms positive ions and negative ions.

The negative ions are the OH- ions, which cause a solution to become alkaline and the positive ions are the H+ ions, which cause a solution to become acidic.

Pure water has a pH of 7, but most ocean water is, on average, about 8, which means it is slightly alkaline. Ocean water is slightly alkaline because there are more hydroxyl ions (OH-) than hydrogen ions (H+) in the water.

Chart: Concentration of hydrogen ions compared to distilled water Examples of solutions at this pH 10,000,000 pH = 0, battery acid, strong hydrofluoric acid 1,000,000, pH=1, hydrochloric acid secreted by stomach lining 100,000, pH 2, lemon juice, gastric acid, vinegar 10,000, pH=3, grapefruit, orange juice, soda 1,000, pH = 4, tomato juice, acid rain 100, pH 5, soft drinking water, black coffee 10, pH = 6, urine, saliva 1, pH 7, "pure" water 1/10, pH 8, sea water 1/100, pH = 9, baking soda 1/1,000, pH=10, Great Salt Lake, milk of magnesia 1/10,000, pH = 11, ammonia solution 1/100,000, pH = 12. soapy water 1/1,000,000, pH = 13, bleaches, oven cleaner 1/10,000,000, pH = 14, liquid drain cleaner The scale is courtesy of The Pacific Institute for the Mathematical SciencesOcean water also contains buffers, which are chemicals to help stabilize the pH of water. The definition of a buffer is "a substance that lessens the tendency of a solution to become too acidic or too alkaline." One such buffer found in ocean water is carbonate (CO3-). Carbonate is formed by the reaction of carbon dioxide and water. Look at the chemical reaction below. The carbonate buffer can absorb free hydrogen ions to stabilize the ocean water at a pH of 8.

LaTeX: CO_2 + H_2O\;^\leftharpoonup_\rightharpoonup H_2CO_3 + {H^+} ^\leftharpoonup_\rightharpoonup {CO_3}^2 + 2H^+CO2+H2O↼⇀H2CO3+H+↼⇀CO32+2H+

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