16.2.2 CIA Demonstration: Natural Acid-Base Indicators

Question 1

CIA Demonstration: Natural Acid-Base Indicators

Answer 1

• A number of natural compounds can serve as pH indicators, including the flowers of Hydrangea macrophylla and the leaves of red cabbage.
• The color change in a red cabbage extract indicates whether a substance is a strong base, a weak base, neutral, a weak acid, or a strong acid.

Question 2

note

Answer 2

• A number of natural compounds can serve as pH indicators.
• For example, the flowers of Hydrangea macrophylla are either bluish white or pink, depending on the pH of the soil.
• Similarly, the color of the leaves of red cabbage depends on the pH.
• An extract made from red cabbage leaves can be used to test the pH of a number of household substances.
• When drain cleaner (sodium hydroxide, NaOH) is added to the extract, the solution turns green. This color indicates that drain cleaner is a strong base.
• When baking soda (sodium bicarbonate, NaHCO 3 ) is added to the extract, the solution turns blue. This color indicates that baking soda is a weak base.
• When vinegar (acetic acid, CH 3 COOH) is added to the extract, the solution turns pink. This color indicates that vinegar is a weak acid.
• When hydrochloric acid (HCl, found in stomach acid) is added to the extract, the solution turns red. This color
  indicates that stomach acid is a strong acid.