Problem
pH LAB
The pH scale is a useful quantification tool that uses a log scale to report concentrations of H+ and OH- ions. (The pH abbreviation stands for the "power of hydrogen," and the abbreviation uses a lowercase p and a capital H.).
Acids are found on the low end of the scale and bases (also called alkalis) are found on the higher end of the scale. Neutrals are found in the middle. Strong acids are corrosive, while strong bases are caustic. Bases often have a slippery or soapy quality to them. Strong bases such as bleach and ammonia may serve as good disinfectants, but can cause death if consumed.
Steps
• Draw a horizonal line across a sheet of paper. Under the line, write the numbers zero through fourteen. Working under the line, label the far left end 0; the middle with a 7, and the far right end a 14. Fill in the whole numbers between 0 and 7 (1, 2, 3, 4, 5, 6) and 7 and 14 (8, 9, 10, 11, 12, 13).**
• Look up the approximate pH ratings of the following items and place them on the scale according to their pH: lemon juice, stomach acid, tomato juice, vinegar (acetic acid), coffee, milk, distilled water, chicken eggs, bleach, ammonia, baking soda, shampoo, hair conditioner, body soap, and skin lotion.
• Repeat Step 1 on the other side of your paper (or below the first pH scale if you have room).
• Repeat Step 2 on your second pH scale with the following materials: calcium carbonate (limestone), human blood, human skin, human hair, beach sand (silica), the soil pH preferred by evergreens, the soil pH preferred by tomatoes, and the soil pH preferred by lilacs.
Task
a) Why do gardeners add calcium carbonate to garden soil if it's acidic?
b) Since the pH scale is a log scale, a pH of 3 is ten times more acidic than a pH of 4, and a pH of 3 is one hundred times more acidic than a pH of 5. How much more basic is a pH of 10 than a pH of 9? How much more basic is a pH of 12 than a pH of 9?