What is Ethanoic Acid? Definition, Formula, and Common Applications
Ethanoic Acid is essential in chemistry and helps students understand various practical and theoretical applications related to this topic. It is widely recognized because of its presence in vinegar and its numerous uses in food, industry, and laboratory experiments.
What is Ethanoic Acid in Chemistry?
A carboxylic acid, ethanoic acid (IUPAC: ethanoic acid; common name: acetic acid) refers to an organic compound containing the –COOH functional group. This concept appears in chapters related to organic acids, food chemistry, and acid-base reactions, making it a foundational part of your chemistry syllabus.
Ethanoic acid is well-known as the main component of vinegar, giving it its sour taste and sharp smell.
Molecular Formula and Composition
The molecular formula of ethanoic acid is CH₃COOH. It consists of two carbon atoms, four hydrogen atoms, and two oxygen atoms, and is categorized under carboxylic acids. The structure features a methyl group (–CH₃) attached to a carboxyl group (–COOH).
The condensed formula is CH₃COOH and the structural formula shows a clear separation between the acid group and the methyl group, making it easy to identify in exam diagrams.
Preparation and Synthesis Methods
Ethanoic acid can be prepared by both industrial and laboratory methods. Industrially, the most common preparation method is the carbonylation of methanol, where methanol reacts with carbon monoxide in the presence of a metal catalyst to produce acetic acid.
In the laboratory, ethanoic acid can also be obtained by oxidizing ethanol (alcohol) using potassium dichromate as an oxidizing agent. These methods highlight its vast production and use in the chemical industry.
Physical Properties of Ethanoic Acid
The key physical properties of ethanoic acid are:
- Appearance: Colourless liquid
- Odor: Pungent, vinegar-like smell
- Boiling Point: 118°C
- Melting Point: 16°C (pure ethanoic acid is called “glacial acetic acid” as it can freeze in cool weather)
- Density: 1.05 g/cm³
- Solubility: Highly soluble in water and many organic solvents
- pKa: 4.76 (shows it is a weak acid)
- Molecular Weight: 60.05 g/mol
Chemical Properties and Reactions
Ethanoic acid displays classic properties of carboxylic acids and participates in important chemical reactions:
- Acid–Base reaction: Reacts with bases such as sodium hydroxide to form sodium ethanoate and water.
CH₃COOH + NaOH → CH₃COONa + H₂O - Reaction with carbonates: Produces carbon dioxide, water, and a salt.
CH₃COOH + Na₂CO₃ → 2CH₃COONa + CO₂ + H₂O - Esterification: Reacts with alcohol (like ethanol) to form esters such as ethyl ethanoate.
CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O - Hydrogen bonding: Forms dimers through hydrogen bonds, resulting in a relatively high boiling point.
Frequent Related Errors
- Confusing ethanoic acid with neutral molecules or other acids like methanoic acid.
- Ignoring the polarity and hydrogen bonding of ethanoic acid, which affects its boiling and melting point.
- Using incorrect names (for example, calling it only “acetic acid” in questions needing the IUPAC name).
- Writing the wrong molecular formula and omitting the carboxyl group in structural drawings.
Uses of Ethanoic Acid in Real Life
Ethanoic acid is widely used in industries like food, pharma, plastics, and textiles. It is also found in household vinegar (5–8% solution in water), used as a food preservative and flavouring agent. Other uses include:
- Making synthetic fibres and polymers (such as acetate rayon)
- Manufacturing esters for flavors and perfumes
- Laboratory reagent for titrations and buffer solutions
- Medical antiseptics and antifungal preparations
Relation with Other Chemistry Concepts
Ethanoic acid links closely with topics like Carboxylic Acids and Esterification. It helps students understand functional groups, acid-base neutralization, and the importance of hydrogen bonding.
Learning about ethanoic acid provides a foundation for recognizing acids, salts, and relevant chemical reactions across organic chemistry.
Step-by-Step Reaction Example
1. Start with the reaction between ethanoic acid and ethanol.Write the balanced equation:
CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O
2. Explain each intermediate or by-product.
In the presence of a strong acid catalyst (like concentrated H₂SO₄) and with gentle heating, ethanoic acid combines with ethanol to form ethyl ethanoate (an ester) and water as by-product.
Lab or Experimental Tips
Remember ethanoic acid by its familiar vinegar smell and its tendency to freeze in winter (forming glacial acetic acid). Vedantu educators often use the tip “vinegar = ethanoic acid solution” to help students link daily life observations with chemistry theory.
Try This Yourself
- Write the IUPAC name of CH₃COOH.
- Identify if CH₃COOH is acidic or basic in water.
- Give two real-life examples of ethanoic acid applications.
Final Wrap-Up
We explored ethanoic acid—its structure, properties, reactions, and real-life importance. For more in-depth explanations and exam-prep tips, explore live classes and notes on Vedantu.
Studying ethanoic acid builds a strong foundation for advanced organic chemistry and helps in understanding many practical applications.
FAQs on Ethanoic Acid – Formula, Structure, Properties & Everyday Uses
1. What is the chemical formula of ethanoic acid?
Ethanoic acid has the chemical formula CH3COOH.
• It is also known as acetic acid.
• The formula shows the presence of a carboxyl group (-COOH) attached to a methyl group.
• This formula is frequently used in exams and practicals.
2. Is ethanoic acid the same as vinegar?
Yes, ethanoic acid is the main component of vinegar.
• Vinegar is a dilute solution (4-8%) of ethanoic acid in water.
• It gives vinegar its characteristic sour taste and strong smell.
• The terms 'acetic acid' and 'ethanoic acid' refer to the same organic compound.
3. What are the uses of ethanoic acid?
Ethanoic acid is used widely in daily life and industry.
• Main ingredient in vinegar for food preservation and flavor.
• Used in the manufacture of acetic anhydride, esters, and synthetic fibers.
• Employed as a laboratory reagent and as a cleaning agent.
• Utilized in medicines (e.g., topical antifungal treatments).
4. What is the boiling point of ethanoic acid?
The boiling point of pure ethanoic acid is 118°C (244°F).
• It can form hydrogen-bonded dimers, resulting in a relatively high boiling point compared to other organic acids of similar molar mass.
• This property is important for laboratory handling and storage.
5. Is ethanoic acid harmful?
Concentrated ethanoic acid can be corrosive and irritating.
• Can cause burns on skin and eye irritation.
• Inhalation of vapors may affect the respiratory system.
• Dilute ethanoic acid (as in vinegar) is safe for consumption in moderation.
• Always handle with proper laboratory precautions.
6. What is glacial acetic acid?
Glacial acetic acid is pure, undiluted ethanoic acid.
• It is called "glacial" because it solidifies just below room temperature (melting point: 16.6°C).
• Appears as clear, ice-like crystals.
• Commonly used in laboratories and industry for chemical synthesis.
7. How does ethanoic acid react with alcohols?
Ethanoic acid reacts with alcohols to form esters and water.
• This process is called esterification.
• Example: CH3COOH + C2H5OH → CH3COOC2H5 + H2O.
• Esters have pleasant fragrances and are used in perfumes and flavorings.
8. What is the structure of ethanoic acid?
Ethanoic acid (CH3COOH) consists of a methyl group (CH3-) attached to a carboxyl group (-COOH).
• The Lewis structure shows two oxygen atoms bonded to the central carbon in the carboxylic group.
• It is represented as:
H
|
H - C - C = O
| |
H OH
• Clear diagrams help in board and entrance exam preparation.
9. What is the functional group present in ethanoic acid?
Ethanoic acid contains the carboxyl group (-COOH) as its functional group.
• The carboxyl group is responsible for the acidic properties of ethanoic acid.
• It undergoes reactions like neutralization, esterification, and redox.
10. Can ethanoic acid act as a preservative?
Yes, ethanoic acid is an effective preservative.
• Its acidity inhibits microbial growth in foods such as pickles, sauces, and vinegar-based preparations.
• It is used widely in the food industry for preservation due to its safety and effectiveness.
11. What is the pKa value of ethanoic acid?
The pKa value of ethanoic acid is approximately 4.76.
• This value indicates that ethanoic acid is a weak acid.
• It partially ionizes in water, making it less corrosive than strong acids.
12. Why is ethanoic acid called a weak acid?
Ethanoic acid is considered a weak acid because it only partially dissociates in water.
• It does not release all of its hydrogen ions in solution.
• This property distinguishes it from strong acids like hydrochloric acid (HCl).
