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

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  • Last Updated : 21 Jun, 2022

Carbon is a nonmetallic, tetravalent element that is of great use to humans. Its name is derived from Latin carbo which means charcoal or ember. Even though carbon is only 0.025% of the earth’s crust and 0.03% in the atmosphere it is of great importance to mankind. Carbon’s abundance and its ability to form polymer at normal is the reason it is commonly found in all living forms.

Stearic Acid

Stearic Acid is a long saturated chain of fatty acids consisting of 18 carbons. It is sometimes even known as Octadecanoic acid due to the presence of 18 carbons in the structure and Stearophanic acid. The name stearic comes from the Greek word stear which means tallow. The salts and esters of stearic acid are collectively known as stearates.

It is found in various animals and plants in a combined form. Naturally, stearic Acid is found as a mixed triglyceride or fat along with many other long-chain acids. It can even be found as an ester of fatty alcohol. Normally it is found more in animal fat when compared to Vegetable fat but this has some exceptions as cocoa butter and shea butter have high quantity of Stearic acid.

Preparation of Stearic acid 

It is made from carbohydrates. Stearic Acid is made from fats and oils by saponification of triglycerides using hot water. The Stearic acid used commercially is a mixture of stearic acid, palmitic acid, and a small quantity of palmitic acid. Though a pure form of Stearic acid can be prepared, commercial use is highly unlikely due to various factors.

Structure of Stearic acid 

The molecular formula of Stearic acid is C2H36O2 or CH3(CH2)16COOH. The IUPAC name of Stearic Acid is Octadecanoic acid.

 

Physical and Chemical Properties of Stearic acid

  • Stearic Acid is present as a white solid.
  • Stearic Acid is odorless in nature.
  • Stearic acid is tallow in taste.
  • The Boiling point of Stearic acid is 721°F at normal pressure.
  • The Melting point of Stearic acid is 156.7°F at normal pressure. The melting point of Stearic acid is high because it is saturated fat and it takes more heat to dissociate the structure.
  • It is insoluble in water and it floats on water.
  • The density o Stearic acid is 0.86°F at normal temperature and pressure.
  • It is stable at normal room temperature and pressure.
  • When it is heated above the boiling point it decomposes to emit acrid smoke and irritating fumes.
  • The pH of Stearic acid is around 5.5. It is a weak acid much like all organic acids.
  • The molecular mass of Stearic acid is 284.48 g/mol.

Uses of Stearic acid 

  • Stearic acid is used as a lubricating agent due to its soft texture.
  • Stearic acid is used in the production of many detergents, soaps, shampoos, and shaving cream products. Easter of Stearic acid is used to produce the pearly effect in soaps and shampoos. 
  • Stearate salts of zinc and calcium are used as heat stabilizers.
  • It is even used as a food additive.
  • Used in food packaging.
  • It is used to make insulators.
  • It is used as a negative plate additive in lead-acid batteries.
  • It is used in the manufacturing of Candles.
  • It is used in coating metals like aluminum and iron with the help of electrolytic plating.

Sample Questions 

Question 1: What are the molecular formula and IUPAC name of Stearic Acid?

Answer: 

The molecular formula of Stearic acid is C2H36O2 or CH3(CH2)16COOH. The IUPAC name of Stearic Acid is Octadecanoic acid.

Question 2: Explain the physical structure of Stearic acid.

Answer: 

Stearic Acid is present as a white solid. Stearic Acid is odorless in nature. Stearic acid is tallow in taste. It is stable at normal room temperature and pressure.

Question 3: What are the boiling and melting point of Stearic acid?

Answer:

The Boiling point of Stearic acid is 721°F at normal pressure. The Melting point of Stearic acid is 156.7°F at normal pressure. The melting point of Stearic acid is high because it is saturated fat and it takes more heat to dissociate the structure. When it is heated above the boiling point it decomposes to emit acrid smoke and irritating fumes.

Question 4: How is Stearic acid prepared?

Answer: 

It is made from carbohydrates. Stearic Acid is made from fats and oils by saponification of triglycerides using hot water. The Stearic acid used commercially is a mixture of stearic acid, palmitic acid, and a small quantity of palmitic acid.

Question 5: What is the main source of Stearic acid?

Answer: 

Naturally, stearic Acid is found as a mixed triglyceride or fat along with many other long-chain acids. It can even be found as an ester of fatty alcohol. Normally it is found more in animal fat when compared to Vegetable fat but this has some exceptions as cocoa butter and shea butter have high quantity of Stearic acid.

Question 6: List some uses of stearic acid.

Answer: 

Stearic acid is used as a lubricating agent due to its soft texture. Stearic acid is used in the production of many detergents, soaps, shampoos, and shaving cream products. Easter of Stearic acid is used to produce the pearly effect in soaps and shampoos. Stearate salts of zinc, and calcium are used as heat stabilizers. It is even used as a food additive. Used in food packaging.

Question 7: Is Stearic acid soluble in water.

Answer: 

The pH of Stearic acid is around 5.5. It is a weak acid much like all organic acids. The molecular mass of Stearic acid is 284.48 g/mol.

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