To Find the pH of Samples Using Indicators (Class 10 Chemistry Practical)
To determine the pH of various solutions and classify them as acidic, basic, or neutral using indicators.
TL;DR: To determine the pH of various solutions and classify them as acidic, basic, or neutral using indicators.
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Aim: To determine the pH of various solutions and classify them as acidic, basic, or neutral using indicators.
Materials Required
- Distilled water
- Dilute acids (HCl, acetic acid)
- Dilute bases (NaOH, ammonia)
- Samples (lemon juice, soap solution, milk, salt water)
- pH paper or universal indicator
- Litmus paper (red and blue)
- Test tubes
- Test tube holder
Theory
pH is a measure of hydrogen ion concentration on a scale of 0-14. pH < 7 indicates acidic solutions, pH = 7 indicates neutral solutions, and pH > 7 indicates basic solutions. Universal indicator paper changes color over a range of pH values, while litmus paper only indicates acidic or basic nature.
Procedure
- Collect different sample solutions in separate test tubes
- Using litmus paper: Dip blue litmus paper in each sample - it turns red for acidic solutions. Dip red litmus paper - it turns blue for basic solutions
- Using universal indicator/pH paper: Dip the paper in each solution and compare the color with the provided scale
- Record the pH value for each sample from the color chart
- Arrange samples in order of increasing pH
- Test at least 5-6 different samples
- Note any patterns, such as household acids or bases
Observation
Lemon juice turns blue litmus red (acidic, pH ≈ 2-3). Soap solution turns red litmus blue (basic, pH ≈ 9-10). Distilled water shows neutral pH ≈ 7. Milk is slightly acidic (pH ≈ 6.5). Salt water is neutral to slightly basic depending on salt type.
Result
Different solutions have different pH values, confirming the presence of acids, bases, and neutral substances. The pH scale helps identify the strength of acidity or basicity.
Precautions
- Use clean test tubes for each sample to avoid contamination
- Do not taste any solutions
- Read the pH value by comparing with the provided color chart
- Use distilled water as control for neutral reference
- Handle concentrated acids and bases with care
Viva Questions
What does pH stand for?
pH stands for 'power of hydrogen', measuring the concentration of hydrogen ions in a solution.
What is the pH range for neutral solutions?
The pH range for neutral solutions is 7.0.
How does universal indicator paper differ from litmus paper?
Universal indicator shows a range of pH values through color changes, while litmus paper only distinguishes acidic from basic solutions.
What color does universal indicator turn in basic solutions?
Universal indicator turns blue or purple in basic solutions.
More Class 10 Chemistry Practicals
- To Prepare a True Solution and Observe the Tyndall Effect
- To Study a Double Displacement (Precipitation) Reaction
- To Test Acids and Bases with Indicators
- 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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