Acid - Base Indicator Activity

Preliminary Activity

Objective

Students will determine the effect of common acids and bases on a pH indicator (red cabbage solution).

Background

Students should record information regarding the nature of acids and bases, and the use of pH indicators.

Materials

Procedure

  1. The instructor places the sample solutions in small beakers. Each beaker is labeled with a number or letter.
  2. Place 15 drops of pH indicator in seven wells of the well plate.
  3. In the seven wells with pH indicator, add five drops of liquid from the labeled beakers. The 1st well gets drops from the first beaker, the 2nd well gets drops from the second beaker, etc.
  4. The last well will have nothing added - this is the experimental control.
  5. Be sure to keep track of which wells received which treatment.
  6. If possible use your sense of smell to identify the samples.
  7. Record in a data table: the beaker number/letter, odor, and the color reactions.
  8. Use a chart of showing the pH of common substances to identify the beaker solutions.
  9. Use the chart to estimate the likely pH of each beaker's contents.

Data

Beaker ID Odor Color Probable Beaker solution Inferred pH
1        
2        
3        
4        
5        
6        
7     Nothing added  

Analysis

Make a generalized statement about how red cabbage juice reacts to an acid and a base.