Citric acid is one of the best-known weak organic acids and occurs naturally in citrus fruits such as lemons, oranges, and grapefruits. Due to its sour taste and preservative properties, it has been used for many years in the food, pharmaceutical, medical, and industrial sectors. An important aspect of citric acid research is its reaction with water . This article analyzes this reaction in detail, including its mechanism, the properties of the reaction products, and its diverse applications.
Structure and chemical properties of citric acid
Citric acid, with the chemical formula C₆H₈O₇, is a tricarboxylic acid (TCA) with three carboxyl groups (-COOH) and one hydroxyl group (-OH). These properties determine its following characteristics:
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Characterized by high water solubility.
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It can release hydrogen ions (H⁺) and exhibit acidic properties.
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It can react with metal ions and act as a chelating agent.
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Citric acid reacts with water
When citric acid dissolves in water, a simple but important chemical reaction takes place:
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Citric acid acidifies water primarily by releasing hydrogen ions (protons) into the solution . Since citric acid is a weak acid, not all of its molecules become ions; some remain neutral. This property ensures a pH value of 2 to 3 (the exact value depends on the concentration of citric acid).
Steps for dissolving citric acid in water
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The first step is physical dissolution.
Citric acid crystals or powder disperse in water and come into contact with its molecules. -
Step 2 – Hydrogen bonds:
The carboxyl group (-COOH) and the hydroxyl group (-OH) in citric acid form hydrogen bonds with water molecules. -
Step 3 – The ions dissociate and
the carboxyl groups gradually release protons and are converted into citrate ions (C₆H₇O₇⁻).
Properties of an aqueous citric acid solution
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Acidity : This solution is acidic and can lower the pH of the surrounding environment.
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Acidity: One of the main reasons for its use in the food industry is its slightly acidic content.
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Relative stability : Citric acid solution is stable at room temperature, but can decompose at very high temperatures.
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Buffer capacity : Since citric acid contains several carboxyl groups, it can act as a buffer to control pH changes.
Application of the reaction of citric acid with water
1. In the food industry
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It gives drinks and juices a sour taste .
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Lowering the pH value can prevent the growth of microorganisms.
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Improves the stability and shelf life of food .
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To prevent discoloration of fresh or processed fruit .
2. At the pharmacy
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– Improves the taste of medications, especially syrups and effervescent tablets .
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In some pharmaceutical preparations, the solubility of the active ingredient increases .
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Used in effervescent tablets and vitamin C supplements.
3. In the health and cosmetics industry
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It is used in skincare products because it regulates the pH level and gently exfoliates the skin.
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Used as a pH regulator in shampoos and detergents.
4. In the fields of chemistry and industry
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Used as a chelating agent to remove metal ions from industrial water systems .
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For use in household descalers (especially for limescale deposits).
Safety precautions when handling citric acid solution
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Concentrated citric acid solutions can cause skin and eye irritation .
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Consuming large quantities of this product can lead to irritation of the digestive system .
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When using industrial products or concentrates, wearing gloves and safety goggles is recommended .
Comparison of citric acid with other water-soluble acids
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Compared to hydrochloric acid (HCl)
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Hydrochloric acid is a stronger acid and can be completely ionized in water.
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Citric acid is relatively mild and is widely used in the food industry.
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Compared to acetic acid (CH₃COOH)
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Both are weak organic acids.
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Acetic acid has a strong vinegar smell, while citric acid is tasteless and has a slightly acidic taste.
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In conclusion
The reaction of citric acid with water may seem simple at first glance, but this very reaction is the basis of its widespread use in various industries. From giving beverages a deliciously tangy flavor to its key role in the pharmaceutical and medical industries, and even in industry in general – all of this relies on citric acid’s ability to release protons and form stable acidic solutions .
Therefore, it can be said that a detailed understanding of this reaction is important not only for chemistry and biology students, but also for specialists in the food and pharmaceutical industries, and even for chemical engineers.