To Test Acids and Bases with Indicators (Class 9 Chemistry Practical)
To test the acidic or basic nature of different solutions using natural and chemical indicators.
TL;DR: To test the acidic or basic nature of different solutions using natural and chemical indicators.
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Aim: To test the acidic or basic nature of different solutions using natural and chemical indicators.
Materials Required
- Distilled water
- Acids (HCl, acetic acid)
- Bases (NaOH, ammonia solution)
- Litmus solution (red and blue)
- Turmeric paste/powder
- Red cabbage juice
- Test tubes
- Dropper
Theory
Indicators are substances that change color in the presence of acids or bases due to changes in pH. Litmus paper is the most common indicator. Natural indicators like turmeric and red cabbage juice also change color with pH. Acids turn blue litmus red, while bases turn red litmus blue.
Procedure
- Take 5-6 test tubes and add samples of different solutions (HCl, NaOH, distilled water, lemon juice, soap solution, salt solution)
- Add 2-3 drops of blue litmus solution to each test tube - acidic solutions will turn it red
- Add 2-3 drops of red litmus solution to another set - basic solutions will turn it blue
- Test with turmeric paste by adding a small amount to each solution - turmeric turns black in basic solution
- Test with red cabbage juice - it turns blue-green in basic solution and pink/red in acidic solution
- Observe and record color changes in a table
- Compare results from different indicators
Observation
HCl solution turns blue litmus red (acidic). NaOH solution turns red litmus blue (basic). Distilled water shows no change with either litmus (neutral). Lemon juice is acidic, soap solution is basic, and salt solution is approximately neutral.
Result
Different indicators show characteristic color changes in acidic and basic solutions. The results confirm the acidic or basic nature of test solutions, consistent across different indicators.
Precautions
- Use fresh indicator solutions for accurate results
- Do not mix indicators unless intentionally comparing
- Use distilled water as a control for neutral reference
- Handle acids and bases carefully
- Record observations immediately for accuracy
Viva Questions
What is an indicator?
An indicator is a substance that changes color in the presence of acids or bases.
What color does blue litmus turn in acidic solution?
Blue litmus turns red in acidic solution.
What is the color change of turmeric in basic solution?
Turmeric changes from yellow to black in basic solution.
Why does red cabbage juice change color with acids and bases?
Red cabbage juice contains a natural indicator that changes color due to pH changes.
More Class 9 Chemistry Practicals
- To Prepare a True Solution and Observe the Tyndall Effect
- To Find the pH of Samples Using Indicators
- To Study a Double Displacement (Precipitation) Reaction
- To Verify the Law of Conservation of Mass
- To Study the Effect of Temperature on Reaction Rate
- To Determine Melting and Boiling Points of a Pure Substance
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