Introduction to Ethanol
Ethanol is an organic compound with the chemical formula C₂H₅OH (or CH₃CH₂OH). It is commonly known as ethyl alcohol and is the alcohol present in alcoholic beverages. According to NCERT, ethanol is one of the most important members of the alcohol family and contains a hydroxyl (-OH) functional group attached to a carbon atom.
Key Facts About Ethanol
| Property | Details |
|---|---|
| Chemical Name | Ethanol (Ethyl Alcohol) |
| Molecular Formula | C₂H₅OH |
| Functional Group | Alcohol (-OH) |
| Physical State | Colorless Liquid |
| Odour | Pleasant Characteristic Smell |
| Solubility | Completely Soluble in Water |
| Boiling Point | Approximately 78°C |
| Nature | Neutral Compound |
Structure of Ethanol
An ethanol molecule consists of:
- Two carbon atoms (C)
- Six hydrogen atoms (H)
- One oxygen atom (O)
- One hydroxyl group (-OH)
Structural Formula
CH₃ – CH₂ – OH
The hydroxyl (-OH) group is responsible for the characteristic properties of alcohols.
Preparation of Ethanol
1. Fermentation Method
Ethanol is produced by the fermentation of sugar using yeast.
Chemical Equation
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
Glucose → Ethanol + Carbon Dioxide
2. Industrial Method
Ethanol is manufactured by reacting ethene with steam in the presence of an acid catalyst.
Physical Properties of Ethanol
Important Physical Properties
- Colorless liquid.
- Has a characteristic smell.
- Miscible with water in all proportions.
- Boils at about 78°C.
- Less dense than water.
- Volatile and highly flammable.
Chemical Properties of Ethanol
1. Combustion Reaction
Ethanol burns in air producing carbon dioxide and water.
Equation
C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O + Heat
Observation: A clean blue flame is produced.
2. Reaction with Sodium
Ethanol reacts with sodium metal to produce sodium ethoxide and hydrogen gas.
Equation
2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂
Uses of Ethanol
Ethanol has numerous applications in daily life and industry.
Major Uses of Ethanol
| Use | Description |
|---|---|
| Fuel | Used as biofuel and mixed with petrol. |
| Solvent | Used in medicines, perfumes, paints and varnishes. |
| Pharmaceutical Industry | Used in preparation of medicines and syrups. |
| Sanitizers | Important ingredient in hand sanitizers and disinfectants. |
| Chemical Industry | Used to manufacture acetic acid, esters and other chemicals. |
| Laboratory Use | Used as a preservative and laboratory reagent. |
| Alcoholic Beverages | Main alcohol present in beverages. |
Ethanol as a Fuel
Why Ethanol is Used as Fuel?
- Burns cleanly.
- Produces less pollution.
- Renewable source of energy.
- Can be obtained from plant materials such as sugarcane and corn.
Advantages of Ethanol Fuel
- Eco-friendly.
- Reduces dependence on fossil fuels.
- Produces fewer harmful emissions.
Ethanol in Hand Sanitizers
Ethanol is widely used in sanitizers because:
- It kills many bacteria and viruses.
- Evaporates quickly.
- Helps maintain hygiene.
Most effective sanitizers contain around 60–80% ethanol.
Harmful Effects of Excessive Consumption of Ethanol
Although ethanol has many useful applications, excessive consumption can be harmful.
Effects on Health
- Damage to liver.
- Impaired judgment and coordination.
- Addiction.
- Harmful effects on the nervous system.
Difference Between Ethanol and Ethanoic Acid
| Feature | Ethanol | Ethanoic Acid |
|---|---|---|
| Formula | C₂H₅OH | CH₃COOH |
| Functional Group | -OH | -COOH |
| Nature | Neutral | Acidic |
| Taste | Not Tested in Laboratory | Sour |
| Litmus Test | No Change | Turns Blue Litmus Red |
NCERT Important Points to Remember
- Ethanol belongs to the alcohol family.
- Its molecular formula is C₂H₅OH.
- It contains a hydroxyl (-OH) functional group.
- Ethanol is completely soluble in water.
- It burns with a clean blue flame.
- Ethanol is widely used as a fuel and solvent.
- Bioethanol is considered an environmentally friendly fuel.
- Excessive consumption of ethanol is harmful to health.
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Practice Questions
Short Answer Questions
1. What is ethanol?
Answer: Ethanol is an alcohol with molecular formula C₂H₅OH containing a hydroxyl (-OH) functional group.
2. What is the functional group present in ethanol?
Answer: Hydroxyl group (-OH).
3. Write the molecular formula of ethanol.
Answer: C₂H₅OH.
4. Why is ethanol used as a fuel?
Answer: Because it burns cleanly, produces less pollution, and is renewable.
5. Name two industrial uses of ethanol.
Answer: Manufacturing medicines and perfumes.
Fill in the Blanks
- Ethanol belongs to the __________ family.
Answer: Alcohol - The molecular formula of ethanol is __________.
Answer: C₂H₅OH - Ethanol contains the __________ functional group.
Answer: Hydroxyl (-OH) - Ethanol burns with a __________ flame.
Answer: Blue - Ethanol is completely soluble in __________.
Answer: Water - Ethanol is used in __________ sanitizers.
Answer: Hand - Ethanol can be produced by __________ of sugar.
Answer: Fermentation - Ethanol is also called __________ alcohol.
Answer: Ethyl - Ethanol reacts with sodium to release __________ gas.
Answer: Hydrogen - Ethanol is commonly used as a __________.
Answer: Solvent
Multiple Choice Questions (MCQs)
1. What is the molecular formula of ethanol?
A. CH₄
B. C₂H₅OH
C. CH₃COOH
D. C₂H₄
Answer: B. C₂H₅OH
2. Ethanol belongs to which class of compounds?
A. Aldehydes
B. Ketones
C. Alcohols
D. Esters
Answer: C. Alcohols
3. Which functional group is present in ethanol?
A. -COOH
B. -CHO
C. -OH
D. >C=O
Answer: C. -OH
4. Ethanol is commonly known as:
A. Methyl Alcohol
B. Ethyl Alcohol
C. Acetic Acid
D. Methane
Answer: B. Ethyl Alcohol
5. Ethanol burns with:
A. Yellow Flame
B. Red Flame
C. Blue Flame
D. Green Flame
Answer: C. Blue Flame
6. Ethanol is soluble in:
A. Kerosene
B. Petrol
C. Water
D. Wax
Answer: C. Water
7. Ethanol is used in:
A. Sanitizers
B. Medicines
C. Perfumes
D. All of these
Answer: D. All of these
8. Ethanol can be prepared by:
A. Distillation of Air
B. Fermentation of Sugar
C. Electrolysis of Water
D. Sublimation
Answer: B. Fermentation of Sugar
9. Which gas is produced when ethanol reacts with sodium?
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Chlorine
Answer: C. Hydrogen
10. Ethanol is considered an environmentally friendly fuel because it:
A. Produces heavy smoke
B. Is renewable and cleaner burning
C. Contains sulfur
D. Pollutes more
Answer: B. Is renewable and cleaner burning
Conclusion
Ethanol (C₂H₅OH) is an important alcohol containing a hydroxyl (-OH) functional group. It is widely used as a fuel, solvent, sanitizer ingredient, laboratory chemical, and industrial raw material. Due to its clean-burning nature and renewable sources, ethanol plays a significant role in modern energy and chemical industries.