Introduction
Ethanoic Acid (CH₃COOH) is an important carbon compound belonging to the carboxylic acid family. It is commonly known as acetic acid. The dilute solution of ethanoic acid is the main component of vinegar, which is widely used as a food preservative and flavoring agent.
Ethanoic acid is studied in NCERT Class 10 Science Chapter: Carbon and Its Compounds.
Definition of Ethanoic Acid
- Ethanoic acid is an organic compound with the molecular formula CH₃COOH.
- It contains a carboxyl group (-COOH).
- It is a weak acid but shows acidic properties.
- It has a sour taste and a pungent smell.
Molecular Details
| Property | Value |
|---|---|
| Common Name | Acetic Acid |
| IUPAC Name | Ethanoic Acid |
| Molecular Formula | CH₃COOH |
| Functional Group | Carboxyl (-COOH) |
| Molecular Mass | 60 u |
| Nature | Weak Acid |
Structure of Ethanoic Acid
The structural formula of ethanoic acid is:
CH₃–COOH
Where:
- CH₃ = Methyl group
- COOH = Carboxyl group
Physical Properties of Ethanoic Acid
1. Color
- It is a colorless liquid.
2. Odor
- Has a strong vinegar-like smell.
3. Solubility
- Completely soluble in water.
4. Taste
- Sour in taste.
5. Boiling Point
- Approximately 118°C.
6. Melting Point
- Around 16.6°C.
7. Glacial Ethanoic Acid
- Pure ethanoic acid freezes during winter.
- It forms ice-like crystals.
- Therefore, pure ethanoic acid is called Glacial Acetic Acid.
Chemical Formula and Functional Group
| Component | Representation |
|---|---|
| Molecular Formula | CH₃COOH |
| Functional Group | -COOH |
| Homologous Series | Carboxylic Acids |
The -COOH group is responsible for the acidic nature of ethanoic acid.
Acidic Nature of Ethanoic Acid
Ethanoic acid shows acidic properties because it releases H⁺ ions in aqueous solution.
Acidic Characteristics
- Turns blue litmus red.
- Reacts with metals.
- Reacts with metal carbonates.
- Reacts with bases.
Chemical Reactions of Ethanoic Acid
1. Reaction with Sodium
Ethanoic acid reacts with sodium metal to produce sodium ethanoate and hydrogen gas.
Equation:
CH₃COOH + Na → CH₃COONa + H₂
Observation
- Bubbles of hydrogen gas are released.
2. Reaction with Sodium Hydroxide
Ethanoic acid reacts with sodium hydroxide to form salt and water.
Equation:
CH₃COOH + NaOH → CH₃COONa + H₂O
This is called a neutralization reaction.
3. Reaction with Sodium Carbonate
Equation:
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
Observation
- Carbon dioxide gas is released.
Esterification Reaction
One of the most important reactions of ethanoic acid is esterification.
Definition
When ethanoic acid reacts with an alcohol in the presence of concentrated sulfuric acid, an ester is formed.
Example
Ethanoic Acid + Ethanol → Ethyl Ethanoate + Water
Equation:
CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O
Characteristics of Esters
- Pleasant fruity smell.
- Used in perfumes.
- Used in flavoring agents.
Uses of Ethanoic Acid
Food Industry
- Used in vinegar.
- Acts as a food preservative.
- Used in pickles and sauces.
Chemical Industry
- Manufacturing dyes.
- Production of plastics.
- Preparation of esters.
Medical Field
- Used in pharmaceutical products.
Household Uses
- Cleaning agent.
- Removal of stains and deposits.
Importance of Ethanoic Acid
| Importance | Description |
|---|---|
| Food Preservation | Prevents food spoilage |
| Ester Production | Used to make perfumes and flavors |
| Chemical Manufacturing | Raw material for various chemicals |
| Laboratory Use | Common laboratory reagent |
Key Points to Remember
- Ethanoic acid is also called acetic acid.
- Molecular formula is CH₃COOH.
- Contains the carboxyl (-COOH) functional group.
- Main component of vinegar.
- Pure form is called glacial acetic acid.
- Shows acidic properties.
- Reacts with alcohols to form esters.
- Widely used in food preservation and chemical industries.
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Practice Questions with Answers
1. What is the common name of ethanoic acid?
Answer: Acetic acid.
2. What is the molecular formula of ethanoic acid?
Answer: CH₃COOH.
3. Which functional group is present in ethanoic acid?
Answer: Carboxyl group (-COOH).
4. Why is pure ethanoic acid called glacial acetic acid?
Answer: Because it freezes easily and forms ice-like crystals.
5. What is formed when ethanoic acid reacts with ethanol?
Answer: Ethyl ethanoate (ester) and water.
Fill in the Blanks
- Ethanoic acid is commonly known as ________.
- Answer: Acetic acid
- The molecular formula of ethanoic acid is ________.
- Answer: CH₃COOH
- Ethanoic acid contains the ________ functional group.
- Answer: Carboxyl
- Vinegar contains dilute ________ acid.
- Answer: Ethanoic
- Esterification produces ________.
- Answer: Esters
MCQs (Multiple Choice Questions)
1. What is the common name of ethanoic acid?
A. Methanoic acid
B. Acetic acid
C. Propanoic acid
D. Ethanol
Answer: B. Acetic acid
2. What is the molecular formula of ethanoic acid?
A. CH₄
B. C₂H₅OH
C. CH₃COOH
D. C₂H₆
Answer: C. CH₃COOH
3. Which functional group is present in ethanoic acid?
A. Hydroxyl
B. Aldehyde
C. Carboxyl
D. Ketone
Answer: C. Carboxyl
4. Ethanoic acid is found in:
A. Milk
B. Vinegar
C. Water
D. Petrol
Answer: B. Vinegar
5. Pure ethanoic acid is called:
A. Formic acid
B. Glacial acetic acid
C. Citric acid
D. Carbonic acid
Answer: B. Glacial acetic acid
6. Ethanoic acid turns blue litmus:
A. Green
B. Yellow
C. Red
D. White
Answer: C. Red
7. Ethanoic acid belongs to:
A. Alcohols
B. Carboxylic acids
C. Alkanes
D. Alkenes
Answer: B. Carboxylic acids
8. Ethanoic acid reacts with ethanol to form:
A. Alkane
B. Ester
C. Ketone
D. Alkene
Answer: B. Ester
9. The smell of vinegar is due to:
A. Methane
B. Ethanol
C. Ethanoic acid
D. Propane
Answer: C. Ethanoic acid
10. Which gas is released when ethanoic acid reacts with sodium carbonate?
A. Oxygen
B. Nitrogen
C. Carbon dioxide
D. Hydrogen chloride
Answer: C. Carbon dioxide
NCERT Exam-Oriented Summary
- Ethanoic acid (CH₃COOH) is a carboxylic acid commonly known as acetic acid.
- It is the main constituent of vinegar.
- Contains the -COOH functional group.
- Pure ethanoic acid is called glacial acetic acid.
- Shows acidic properties and reacts with metals, bases, and carbonates.
- Forms esters with alcohols through esterification.
- Used in food preservation, perfumes, medicines, and chemical industries.