1. Aim: To determine the pH value and nature (neutral, acidic, or basic) of different salts using a universal indicator.
2. Requirements: saturated solutions of table salt, soap, washing soda, baking soda, baking powder, plaster of Paris (POP), universal indicator, dropper, and pH chart.
3. Procedure:
- Prepare saturated solutions of each salt in separate containers.
- Add 2–3 drops of the universal indicator to each solution.
- Observe the colour change and compare it with the pH chart to determine the pH value.
- Record the observations in a table, noting the original colour, indicator colour, pH value, and nature of each solution.
4. Observation:
| Salt | Original color (of the solution) | Color on addition of universal indicator | pH value | Nature |
|---|---|---|---|---|
| Table salt | Colorless | Green | 7 | Neutral |
| Soap | Colorless | Blue | >7 | Basic |
| Washing soda | Colorless | Blue | >7 | Basic |
| Baking soda | Colorless | Blue | >7 | Basic |
| Baking powder | Colorless | Green/Yellow | ~7 | Neutral/Acidic |
| POP (Plaster of Paris) | Colorless | Blue | >7 | Basic |
5. Conclusion: Table salt shows a neutral pH of 7. Soap, washing soda, baking soda, and POP are basic, with a pH greater than 7. Baking powder can be neutral or slightly acidic, with a pH around 7. The pH of a salt depends on whether it is derived from a strong or weak acid/base combination. Neutral salts come from strong acid and strong base, acidic salts from strong acid and weak base, and basic salts from weak acid and strong base.
