CLASS 10 CBSE CHEMISTRY PRACTICAL

EXPERIMENT: Study of the Properties of Acetic Acid (Ethanoic Acid)

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AIM:

To study the following properties of acetic acid (ethanoic acid):

• Odour
• Solubility in water
• Effect on litmus
• Reaction with Sodium Hydrogen Carbonate

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MATERIALS REQUIRED:

S. No.	Material	Quantity
1	Glacial acetic acid (CH₃COOH)	5 mL
2	Dilute acetic acid solution	10 mL
3	Distilled water	50 mL
4	Blue litmus paper	2 strips
5	Red litmus paper	2 strips
6	Sodium hydrogen carbonate (NaHCO₃)	1-2 g
7	Test tubes	4
8	Test tube stand	1
9	Test tube holder	1
10	Dropper	2
11	Beaker (100 mL)	1
12	Glass rod	1
13	Burning splinter/matchstick	As required

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THEORY:

Acetic Acid (Ethanoic Acid):

• Chemical Formula: CH₃COOH or C₂H₄O₂
• Molecular Structure: CH₃-COOH (contains carboxyl group -COOH)
• Nature: Weak organic acid belonging to carboxylic acid family
• Common Name: Vinegar (5-8% acetic acid solution)
• Pure Form: Glacial acetic acid (99-100% pure, freezes at 16.6°C)

Properties of Acetic Acid:

1. Physical Properties:

• Colorless liquid
• Characteristic pungent, vinegar-like smell
• Sour taste
• Miscible with water in all proportions
• Boiling point: 118°C
• Melting point: 16.6°C

2. Chemical Properties:

• Acidic Nature: Turns blue litmus red (acidic)
• Weak Acid: Partially ionizes in water: CH₃COOH ⇌ CH₃COO⁻ + H⁺
• Reaction with Carbonates/Bicarbonates: Produces CO₂ gas with effervescence

Important Reactions:

With Sodium Hydrogen Carbonate:

CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂↑
(Acetic acid) + (Sodium hydrogen carbonate) → (Sodium acetate) + (Water) + (Carbon dioxide)

Test for CO₂ gas:

• Turns lime water milky
• Extinguishes a burning splinter

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PROCEDURE:

A. TEST FOR ODOUR:

1. Take a clean and dry test tube (labeled as Test tube 1).
2. Pour about 2 mL of dilute acetic acid into it.
3. Hold the test tube at some distance from your nose.
4. Gently waft the air from the test tube towards your nose using your hand.
5. Do not inhale directly from the test tube.
6. Note the smell/odour.
7. Record your observation.

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B. TEST FOR SOLUBILITY IN WATER:

1. Take a clean beaker and add about 50 mL of distilled water.
2. Take about 2 mL of glacial acetic acid in a test tube (Test tube 2).
3. Add the acetic acid drop by drop to the water in the beaker.
4. Stir gently with a glass rod.
5. Observe whether the acetic acid dissolves in water or forms a separate layer.
6. Touch the outer surface of the beaker to check if any heat is evolved.
7. Record your observation.

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C. TEST FOR EFFECT ON LITMUS:

1. Take two clean test tubes (Test tube 3 and Test tube 4).
2. Pour about 2 mL of dilute acetic acid in each test tube.
3. Dip a strip of blue litmus paper in test tube 3.
4. Dip a strip of red litmus paper in test tube 4.
5. Observe any color change in the litmus papers.
6. Record your observations.

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D. TEST FOR REACTION WITH SODIUM HYDROGEN CARBONATE:

1. Take a clean and dry test tube (Test tube 5).
2. Add a pinch (about 0.5 g) of solid sodium hydrogen carbonate (NaHCO₃) to it.
3. Add about 2-3 mL of dilute acetic acid to the test tube.
4. Observe carefully for:

• Effervescence (bubbles/fizzing)
• Evolution of gas

1. Quickly bring a burning splinter/matchstick near the mouth of the test tube.
2. Observe what happens to the burning splinter.
3. Note the observations.
4. If lime water is available, pass the gas through it and observe.

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OBSERVATIONS:

Table: Properties of Acetic Acid

S. No.	Test Performed	Observation	Inference
1	Test for Odour	Characteristic pungent smell like vinegar	Acetic acid has a distinct vinegar-like odour
2	Test for Solubility in Water	• Acetic acid dissolves completely in water • No separate layer formed • Forms a homogeneous solution • Slight warmth felt (exothermic)	Acetic acid is highly soluble/miscible with water in all proportions
3a	Effect on Blue Litmus	Blue litmus turns RED	Acetic acid is acidic in nature
3b	Effect on Red Litmus	Red litmus remains RED (no change)	Confirms acidic nature
4	Reaction with Sodium Hydrogen Carbonate (NaHCO₃)	• Brisk effervescence observed • Colorless gas evolved • NaHCO₃ dissolves • Burning splinter extinguishes • Lime water turns milky (if tested)	• Acetic acid reacts with NaHCO₃ • Carbon dioxide (CO₂) gas is evolved • Confirms acidic nature

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CHEMICAL EQUATIONS:

1. Ionization in Water:

CH₃COOH (aq) ⇌ CH₃COO⁻ (aq) + H⁺ (aq)
(Acetic acid) → (Acetate ion) + (Hydrogen ion)

2. Reaction with Sodium Hydrogen Carbonate:

CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂↑

Acetic acid + Sodium hydrogen → Sodium acetate + Water + Carbon dioxide
               carbonate                                    (gas)

3. Test for Carbon Dioxide:

CO₂ + Ca(OH)₂ → CaCO₃↓ + H₂O
(Carbon dioxide) + (Lime water) → (Calcium carbonate - white ppt) + (Water)

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RESULT:

The following properties of acetic acid (ethanoic acid) were studied:

1. Odour: Acetic acid has a characteristic pungent, vinegar-like smell.
2. Solubility in Water: Acetic acid is highly soluble in water and mixes in all proportions (miscible).
3. Effect on Litmus:

• Turns blue litmus paper RED
• No effect on red litmus paper
• Conclusion: Acetic acid is acidic in nature

1. Reaction with Sodium Hydrogen Carbonate:

• Reacts with NaHCO₃ producing brisk effervescence
• Evolves carbon dioxide (CO₂) gas
• CO₂ extinguishes burning splinter
• Conclusion: Confirms the acidic nature of acetic acid

Overall Conclusion: Acetic acid is a weak organic acid with characteristic properties including pungent odour, high water solubility, acidic nature (turns blue litmus red), and reacts with carbonates/bicarbonates to produce CO₂ gas.

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PRECAUTIONS:

General:

1. Handle acetic acid (especially glacial acetic acid) carefully as it is corrosive.
2. Avoid direct contact with skin and eyes.
3. Wear safety goggles and gloves if available.
4. Work in a well-ventilated area.
5. Use dilute acetic acid for all tests except solubility test.

Test Specific:

6. For Odour Test:

• Never smell chemicals directly from the container
• Always waft the vapors gently towards your nose
• Keep the test tube at a safe distance

6. For Solubility Test:

• Add glacial acetic acid drop by drop to water (not water to acid)
• Stir gently to avoid splashing
• Use cold water

6. For Litmus Test:

• Use fresh litmus papers
• Dip only the tip of litmus paper in the solution
• Observe color change immediately

6. For Reaction with NaHCO₃:

• Add acetic acid slowly to avoid excessive frothing
• Do not bring burning splinter too close initially
• Hold test tube away from face during reaction

Safety:

10. Do not taste any chemical.
11. Clean all apparatus after use.
12. Dispose of chemicals as per laboratory guidelines.
13. Wash hands thoroughly after the experiment.
14. Report any spills or accidents immediately to the teacher.
15. Keep the test tube tilted slightly away while testing for gas.

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SOURCES OF ERROR:

1. Using concentrated acetic acid instead of dilute may give vigorous reactions
2. Contaminated litmus papers may not show proper color change
3. Moist sodium hydrogen carbonate may not show clear effervescence
4. Expired chemicals may not react properly
5. Improper wafting may not detect odour correctly

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VIVA QUESTIONS:

1. Q: What is the chemical formula of acetic acid?

• A: CH₃COOH or C₂H₄O₂

2. Q: What is the common name of acetic acid?

• A: Vinegar (in dilute form, 5-8% solution)

3. Q: Why is pure acetic acid called glacial acetic acid?

• A: Because it freezes at 16.6°C forming ice-like crystals.

4. Q: Is acetic acid a strong acid or weak acid?

• A: Weak acid (partially ionizes in water)

5. Q: What is the functional group present in acetic acid?

• A: Carboxyl group (-COOH)

6. Q: What type of compound is acetic acid?

• A: Organic acid belonging to carboxylic acid family

7. Q: What gas is evolved when acetic acid reacts with sodium hydrogen carbonate?

• A: Carbon dioxide (CO₂)

8. Q: How do you test for carbon dioxide gas?

• A:
  • It extinguishes a burning splinter
  • It turns lime water milky

9. Q: Why does acetic acid turn blue litmus red?

• A: Because it is acidic in nature and releases H⁺ ions in water.

10. Q: Write the equation for the reaction between acetic acid and sodium hydrogen carbonate.

• A: CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂↑

11. Q: What is the product formed when acetic acid reacts with NaHCO₃?

• A: Sodium acetate (CH₃COONa), water (H₂O), and carbon dioxide (CO₂)

12. Q: Is acetic acid soluble in water?

• A: Yes, it is miscible with water in all proportions.

13. Q: What is the pH range of acetic acid solution?

• A: pH 2-3 for dilute solution (acidic, pH < 7)

14. Q: Name two uses of acetic acid.

• A:
  • As a food preservative (vinegar)
  • In manufacturing of acetate rayon and plastics

15. Q: What happens when acetic acid reacts with sodium hydroxide?

• A: Neutralization occurs forming sodium acetate and water
  • CH₃COOH + NaOH → CH₃COONa + H₂O

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