Definition of Acetic Acid
Acetic acid is a colorless liquid and an organic compound acid. Vinegar contains a minimum of 4% acetic acid by volume, making acetic acid the main component of vinegar aside from water.
Acetic acid is an organic compound with a relatively strong acidic property. This chemical has been produced for a long time and finds numerous applications in food production, industry, and medicine.
Apart from the aforementioned name, this product is also known by other names such as Ethanoic acid, Acetic acid, Hydroxyethanoic acid (HAc), Ethylic acid, Methane carboxylic acid, vinegar, ethanol acid.
Chemical formula: CH3CO2H
Molecular weight: 60
Condensed formula: CH3COOH
It consists of one -OH group bonded to the C=O group, forming the -COOH group. The -COOH (Carboxyl) group is responsible for the acidic nature of the molecule, giving rise to the characteristic chemical properties of acetic acid.
What are the physical properties of acetic acid?
The physical properties of acetic acid are as follows:
- It is a colorless liquid with a sour taste. It is highly soluble in water.
- The density of acetic acid is 1.049 g/cm3 (liquid) and 1.266 g/cm3 (solid).
- The melting point of acetic acid is 16.5 degrees Celsius.
The boiling point of acetic acid is 118.2 degrees Celsius. Its boiling point is higher than that of alcohols with the same molecular weight due to the stronger and more stable hydrogen bonding between the hydroxyl groups. Additionally, the polar nature of the O-H group in acetic acid is stronger than that of ROH (alcohols), resulting in a greater ability to form hydrogen bonds. The boiling points of compounds with the same molecular weight as acetic acid are arranged as follows:
CH3COOH > CH3CH2OH > CH3-COO-CH3 > CH3-CHO > CH3CH2Cl > C2H6
When heated, acetic acid has the ability to dissolve small amounts of sulfur and phosphorus.
The acetic acid molecule is polar, which allows it to dissolve well in polar compounds such as water, as well as in nonpolar compounds like oil, hexane, cellulose, and many other chemical elements such as sulfur and iodine.
The chemical properties of acetic acid are as follows
The hydrogen atom in the carboxyl group has the ability to donate a proton (H+) and gives acetic acid its acidic properties, which determine its chemical behavior.
Acetic acid is a weak acid that exhibits all the characteristics of an acid
To demonstrate that acetic acid is a weak acid, the following experiments are conducted. Acetic acid solution is added to test tubes containing the following substances: litmus paper, phenolphthalein solution with NaOH, CuO, Zn, and Na2CO3.
What are the observed phenomena in these experiments?
The acetic acid solution exhibits acidity by turning litmus paper red. When acetic acid solution is added to the test tube containing Zn, the Zn gradually dissolves, and colorless gas is released from the solution. Equation:
Zn + 2CH3COOH → (CH3COO)2Zn + H2↑
When acetic acid solution is added to the test tube containing CuO, the CuO powder gradually dissolves, and the solution changes from colorless to blue. Equation:
CuO + 2CH3COOH → (CH3COO)2Cu + H2O
When acetic acid solution is added to the test tube containing NaOH with phenolphthalein, the pink color of the solution in the test tube disappears. Equation:
NaOH + CH3COOH → CH3COONa + H2O
When acetic acid solution is added to the test tube containing Na2CO3, the Na2CO3 gradually dissolves, and colorless gas is released from the solution. Equation:
Na2CO3 + 2CH3COOH → 2CH3COONa + CO2↑ + H2O
From these experiments, we can conclude the following chemical properties of acetic acid:
Acetic acid is an organic acid with the characteristics of an acid. However, it is a weak acid and belongs to the group of monoprotic acids.
Acetic acid reacts with bases, carbonates, and bicarbonates. When reacting with these substances, the resulting products are the corresponding metal acetates, water, and carbonic acid. The most common example is sodium bicarbonate with vinegar. Equation:
NaHCO3 + CH3COOH → CH3COONa + CO2 + H2O
Acetic acid reacts with alkalis to produce water and metal ethanoates. Equation: NaOH + CH3COOH → CH3COONa + H2O
When acetic acid is decomposed at temperatures above 440 degrees Celsius, it forms carbonic acid, methane, or ethenone and water.
Acetic acid reacts with metals that are above hydrogen in the reactivity series, liberating hydrogen gas. Acetic acid has the ability to corrode various metals to form hydrogen gas and acetate salts. For example, when it reacts with magnesium, the chemical equation is:
Mg + 2CH3COOH → (CH3COO)2Mg + H2
Aluminum is passive with acetic acid because during the reaction, a thin layer of aluminum oxide forms on the surface to prevent further chemical corrosion. That’s why aluminum containers are commonly used to store acetic acid.
Acetic acid reacts with weaker acids, for example:
2CH3COOH + CaCO3 → (CH3COO)2Ca + CO2 + H2O
Acetic acid reacts with ethyl alcohol
To investigate how acetic acid reacts with ethyl alcohol, the following experiment is conducted. Ethyl alcohol and acetic acid are added to test tube A, and a small amount of concentrated sulfuric acid is added as a catalyst. The mixture is then heated to boiling for a period of time and subsequently removed from heat. A small amount of water is added to the condensed liquid in test tube B, gently shaken, and then observed.
After a certain period of time, the following observations are made: Test tube B contains a colorless liquid with a pleasant odor. It is insoluble in water and floats on the surface of the water.
Thus, ethyl alcohol reacts with acetic acid to produce ethyl acetate. This is a liquid with a pleasant odor and low solubility in water, commonly used as a solvent in industries.
The reaction can be represented by the chemical equation:
C2H5OH + CH3COOH ⇄ CH3COOC2H5 + H2O (in the presence of concentrated sulfuric acid, at elevated temperature)
Methods of acetic acid synthesis
Currently, there are various methods for synthesizing acetic acid. These methods include:
Synthesis of acetic acid from ethyl alcohol
To produce vinegar, a common method involves fermentation of a dilute solution of ethyl alcohol, following the equation:
CH3CH2OH + O2 → CH3COOH + 2H2O (catalyst: Acetobacter)
Note: Organic compounds with the molecular group -COOH, having the general formula CnH2n + 1COOH, are referred to as monofunctional saturated carboxylic acids, exhibiting similar properties to acetic acid.
In the industry, commercial acetic acid is often produced from butane (C4H10) through catalytic oxidation at a specific temperature, according to the equation:
2C4H10 + 5O2 → 4CH3COOH + 2H2O (catalyst, temperature)
Butane Acetic acid
Important Applications of Acetic Acid
The global demand for acetic acid is approximately 6.5 million tons per year. Here are some of the most important and common applications of acetic acid in daily life.
Applications of Acetic Acid in Industry
Approximately 40% to 45% of the global production of acetic acid is used in the manufacturing of vinyl acetate monomer, a adhesive and paint material.
Used as a solvent or for mild acidity.
Vinegar, which is a 5-7% acetic acid solution, is widely used in the food industry for processing canned goods, vegetables, fruits, and seasonings.
Used as a descaling agent for water pipes and kettle.
Acetic acid is used in the textile dyeing, rubber, and electroplating industries.
Applications of Acetic Acid in Medicine
Acetic acid has effective antibacterial properties and is used as a disinfectant (diluted to a concentration of 1%). It can be utilized as an alternative product to prevent infection and kill bacteria.
Acetic acid is formulated into diabetes medications.
Applications of Acetic Acid in Human Health (at concentrations of 4-8%)
Acetic acid inhibits the enzymatic breakdown of complex carbohydrates into simple sugars, helping to reduce postprandial blood sugar levels and contribute to weight loss.
Apple cider vinegar aids in preventing the accumulation of fat in the body and liver, reducing daily calorie intake, thereby assisting in fat reduction.
Apple cider vinegar is an effective remedy for anti-aging.
Acetic acid is an organic acid with characteristic acid properties and reacts with metals to form neutral salts. This ability of acetic acid helps in dissolving kidney stones.
Is Acetic Acid Toxic? How Does It Affect Human Health?
Chemical experts state that acetic acid itself is not toxic to the human body, but if consumed in large doses, it can lead to fatality.
Respiratory Effects: Inhaling a large amount of acetic acid can cause irritation to the nose, throat, and lungs, resulting in severe damage to the lining of the respiratory organs and potentially leading to difficulty breathing.
Skin Irritation: Contact with the skin can cause irritation, such as pain, redness, and blisters, with more severe cases leading to burns after a few minutes of contact.
Life-Threatening: Swallowing acetic acid can cause severe corrosion of the mouth and digestive tract, resulting in vomiting, diarrhea, circulatory collapse, kidney damage, and even death.
Vinegar is a sour-tasting liquid formed through fermentation and has many health benefits. Acetic acid only accounts for a small percentage (from 3 to 5%) of vinegar, contributing to its sour taste. However, if vinegar is produced by diluting water with industrial-grade acetic acid, it can be harmful to human health.
Vinegar contains various nutrients, including vitamins, amino acids, and organic acids, which provide numerous health benefits. However, to ensure safety when using vinegar, consumers need to be cautious in selecting food-grade vinegar from reputable sources. Additionally, they can consider fermenting their own vinegar at home for personal use.
This article has provided comprehensive information about the formula, properties, applications, and some practical exercises involving acetic acid—a widely used substance in our surroundings. Stay tuned to the Basic Knowledge section of Goodheathplan to explore more useful knowledge in the fields of Chemistry, Mathematics, Physics, and more.
Johnny Jacks was born in 1985 in Texas, USA. He is the founder of Good Health Plan and is passionate about helping people improve their health and physical well-being. With over a decade of experience working in the healthcare industry, he currently works at Goodheathplan.com – a blog that shares knowledge on beauty and health.