CHM 122 Mini Experiment – pH of household chemicals Ms Dang Name

Due date: No later than Wednesday 5/28/14. NO EXCEPTIONS

Students will be rewarded with 20 points extra credit toward the HW/Quizzes

The pH of a solution can be accurately measured by a pH meter. Although less precise, acid-base indicators are often used to measure pH because they change color with a small pH range. Red cabbage juice contains a natural pH indicator that changes colors according to the acidity of the solution. Red cabbage juice indicator is easy to make, exhibits a wide range of colors, and can be used to make your own pH paper strips

What You Need to Do the Experiment

  • A head of red cabbage
  • A stove
  • A pot
  • water
  • A medicine cup with teaspoon or milliliter markings
  • Several small paper cups
  • 5-6 test substances (e.g., lemon juice, clear sports drink, lemon-lime soda, window cleaner, vinegar).

Procedure

Part 1

  1. Chop the cabbage into small pieces until you have about 2 cups of chopped cabbage. Place the cabbage in a pot or other clear container and add boiling water to cover the cabbage. Allow at least ten minutes for the color to leach out of the cabbage. (Alternatively, you can place about 2 cups of cabbage in a blender, cover it with boiling water, and blend it.)
  2. Filter out the plant material to obtain a red-purple-bluish colored liquid. This liquid is at about pH 7. (The exact color you get depends on the pH of the water.)
  3. Prepare a set of 6 household chemical products in a clear cup or small paper cup. If the household product(s) are solid then dissolve them in water before adding the cabbage juice.
  4. Add a few (3-4) drops or 1 teaspoon of cabbage indicator to each product and observe the color change.

Part 2:

  1. Prepare three mixtures that have the following sample
  2. Water and acid sample
  3. Water and basic sample
  4. Acid and basic sample
  5. Add a few drops of cabbage juice to those mixtures and observe the color change. Determine whether solution (a), (b), (c) is/are buffer.

Report

Provide a data table with all information to support your experiment. (E.g: Identity, color of substances before and after adding the indicator, the approximated pH and the concentration of H3O+). Then write a 1-2 pages summary about this experiment and your conclusion on using cabbage juice as a pH indicator for those household products. You must include a picture of the result of your experiment. Use the picture below as a reference for pH 1 to pH14 solutions.