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Citric Acid Formula – Structure, Properties, Uses, Sample Questions

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  • Last Updated : 14 Mar, 2022

Citric Acid is a strong organic compound but weak organic acid with a chemical formula C6H8O7. Citric acid is present in two forms – monohydrate or water-free (anhydrous). This acid is usually found in various vegetables and fruits like lemons, oranges, the tomato has a higher amount of citric acid. It is also called tribasic acid. 

Citric Acid 

Citric acid is odorless, sour in taste, and appears as a white crystalline solid. It has a monoclinic crystal structure. This acid was isolated for the first time by chemist Carl Wilhelm Scheele in the year 1784. Somehow it is similar in resemblance to table salt it is sold in the market as sour salt.

Citric Acid Formula

Citric acid can be defined as a tricarboxylic acid, i.e., propane-1, 2, 3-tricarboxylic acid with a hydroxy substituent at position C–2.

Citric acid is generally present naturally in citrus fruits. In this biochemistry well it is known as the intermediate cause involved in the citric acid cycle, which occurs or is found in the metabolism of all aerobic organisms. As you can taste their presence in citrus fruits like lemons and lime that contain a high volume of citric acid. Citric acid can take up to 8% of the fruit’s total dry weight.

Structure of Citric acid 

 Molecular Formula = C6H8O7 and its IUPAC name = 2-hydroxypropane-1, 2, 3-tricarboxylic acid

 The Simplified molecular-input line-entry system=  OC(=O)CC(O)(CC(O)=O)C(O)=O

Structure of citric acid

Physical properties of citric acid

Chemical Formula of Citric acid           C6H8O7
Extended Formula of citric acidHOC(CO2H)(CH2CO2H)2
Molar Mass / Molecular Weight192.124gmol–1
Density of Citric acid 1.665gcm–3
Boiling Point of Citric acid310°C
Melting Point of Citric acid153°C
Solubility of Citric acidSoluble in water, alcohol, ether, acetone.

Uses of Citric Acid 

  1. Citric acid is mostly used in foods and beverages such as soft drinks, juices, etc. It gives them a tangy, citrus taste. Citric is highly used as a flavoring agent.
  2. It acts as a food preservative because its acidic pH inhibits the growth of many bacteria on food, thus preventing them from getting spoiled. citric acid is lowering the pH making oxidative enzymes inactive in frozen foods,
  3. Citric acid is used in the manufacturing of soaps and detergents to soften their basic pH.
  4. It is also used in many cosmetic products as a preservative to maintain acid-base pH balance. It is useful in cosmetics to remove dead skin, it also diminishes wrinkles and improves skin tone.
  5. Citric acid acts as an anticoagulant by chelating calcium in the blood and is also used as an acidulant to control pH levels.
  6. In diseases like osteoporosis, lemon peels, as a source of citric acid, are used to improve bone health as they contain a high amount of calcium and vitamin C, which assist in the maintenance of bones.
  7. Citric acid is used as a preservative for storing blood in the pharmaceutical industry.
  8. Citric acid is used as an emulsifier by some ice companies, to refrain the fat globules as an emulsifying agent.
  9. Citric acid is used in caramel for sucrose crystallization.

Conceptual questions

Question 1: Identify citric acid as basic or acidic?

Answer: 

Citric Acid is a strong organic compound but weak organic acid with a chemical formula C6H8O7. It is an acidic compound because It turns blue litmus paper to red. It is a weak organic acid.

Question 2: Give some side effects of citric acid?

Answer: 

Citric acid is good for the health but excessive exposure to citric acid may lead to tooth decay, acidic stomach, numbness, muscle twitching or cramps .

It also shows rapid weight gain or swelling in the body, fast or slow heart rate, sudden mood changes, diarrhoea, convulsions are other associated side effects caused due to overdose of citric acid.

Question 3: How to prepare a solution of citric acid?

Answer: 

Combine citric acid crystals (sometimes referred to as sour salt) can be prepared with 1 or 2 points of distilled boiling water per pound of citric acid to form the citric acid solution. After that, put the crystals of citric acid in a non-metal bowl and gradually pour the boiling water into the bowl, stirring with a non-metal spoon.

Question 4: Does the body can absorb citric acid?

Answer: 

The guts absorb citric acid after oral administration and It also enhances the bioavailability of minerals and helps the body to absorb them efficiently.

Question 5: What are the substitutes for citric acid?

Answer: 

The substitute of citric acid is found in every household and it is lemon juice. Another substitute is tartaric acid .

Question 6: What is the boiling and melting point of Citric Acid?

Answer: 

  1. The boiling point of citric acid is 310°C
  2. The melting point is 153°C

Question 7: Why citric acid is used as a disinfectant?

Answer:  

It is used as disinfectant because It is helpful for the general disinfection and cleaning because it kills bacteria, mould, and mildew. It is also used in removing hard water stains  or soap scum etc and also used as preservative.

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