Olfactory indicators in Acids, Bases and Salts – Class 10 Science Experiment

Chapter Name: Acids, Bases and Salts

Activity Name: Olfactory indicators in Acids, Bases and Salts

Activity Description:

This experiment aims to use olfactory indicators to identify acidic and basic solutions. Dilute solutions of various substances such as hydrochloric acid, sulphuric acid, nitric acid, acetic acid, sodium hydroxide, calcium hydroxide, magnesium hydroxide, ammonium hydroxide, and potassium hydroxide are prepared.

These solutions are then tested using different indicators such as blue litmus paper, red litmus paper, methyl orange, and phenolphthalein to observe and record the color changes.

Required Items:

1. Hydrochloric acid (HCl)
2. Sulphuric acid (H2SO4)
3. Nitric acid (HNO3)
4. Acetic acid (CH3COOH)
5. Sodium hydroxide (NaOH)
6. Calcium hydroxide [Ca(OH)2]
7. Magnesium hydroxide [Mg(OH)2]
8. Ammonium hydroxide (NH4OH)
9. Potassium hydroxide (KOH)
10. Blue litmus paper
11. Red litmus paper
12. Methyl orange
13. Phenolphthalein
14. Four watch glasses

Step by Step Procedure:

1. Prepare dilute solutions of each substance listed above.
2. Take four watch glasses and place one drop of each dilute solution into separate watch glasses.
3. Test each solution as follows: a. Dip blue litmus paper in the first watch glass. b. Dip red litmus paper in the second watch glass. c. Add a drop of methyl orange to the third watch glass. d. Add a drop of phenolphthalein to the fourth watch glass.
4. Observe and note down the respective color changes in the chart provided.

Experiment Observations:

• Record the color changes observed for each substance with the different indicators in the chart provided during the experiment.

Note down your observations in table format:

Precautions:

1. Handle acids and bases with care, wearing appropriate safety equipment like gloves and safety goggles.
2. Perform the experiment in a well-ventilated area to avoid inhaling any fumes.
3. Use a small amount of solutions in the watch glasses to prevent wastage and spilling.
4. Avoid touching the indicators directly with hands to prevent contamination.
5. Dispose of the solutions properly according to the laboratory guidelines.

Lesson Learnt from Experiment:

The experiment demonstrates the use of olfactory indicators to identify acidic and basic solutions. Olfactory indicators are substances whose odors change in acidic or basic media, and they can provide a simple and quick way to determine the nature of a solution without using complex equipment.