Difference Between Borax and Boric Acid

Main Difference – Borax vs Boric Acid

Borax and boric acid are two different compounds consist of boron atoms along with some other chemical elements. Borax is a common name used to name sodium borate. They have different chemical and physical properties depending on their chemical composition. Borax is a mineral. It is a salt of boric acid. Boric acid is a weak, monobasic Lewis acid of boron. It has many applications such as use as an insecticide, antiseptic, flame retardant, etc. The main difference between borax and boric acid is that the chemical formula of borax is Na₂B₄O₇·10H₂O whereas the chemical formula of boric acid is BH₃O₃.

Key Areas Covered

1. What is Borax
– Definition, Chemical Data, Uses
2. What is Boric Acid
– Definition, Chemical Data, Uses
3. What is the Difference Between Borax and Boric Acid
– Comparison of Key Differences

Key Terms: Borax, Boric Acid, Boron, Hydrogen Borate, Lewis Acid, Mineral, Sodium Borate, Sodium Tetraborate Decahydrate, Trihydrooxidoboron

What is Borax

Borax is a natural mineral having the chemical formula Na₂B₄O₇·10H₂O. It is also known as sodium borate. However, the IUPAC name of this compound is Sodium tetraborate decahydrate. It is a very important compound formed by boron.

The molar mass of borax is 381.38 g/mol when hydrated and 201.22 g/mol when dehydrated. It appears as a white solid. It is composed of soft, colorless crystals that are easily dissolved in water. The crystal structure is monoclinic prismatic. The melting point of borax is 743 °C, and the boiling point is 1,575 °C.

The term borax is used to name several closely related compounds of sodium borate. But it is usually used for hydrated sodium borate having 10 water molecules per sodium borate unit (sodium tetraborate decahydrate). When considering the chemical structure of this compound, there are two types of boron atoms: two of the four boron atoms form four coordinate bonds whereas the other two boron atoms form only three coordinate bonds. They have tetrahedral structures and triangle structures respectively.

Figure 1: Borax Solid Compound

Uses of Borax

Borax is used as a,

Insecticide
Fungicide
Herbicide
Desiccant
Household cleaner
Food preservative

What is Boric Acid

Boric acid is a Lewis acid of boron having the chemical formula BH₃O₃. It is also called hydrogen borate. But IUPAC name of boric acid is Trihydrooxidoboron. It exists as colorless crystals or as a white powder.

The molar mass of boric acid is 61.83 g/mol. The melting point of boric acid is 170.9 °C, and the boiling point is 300 °C. The chemical structure of boric acid has a trigonal planar structure. Since boron has only three unpaired electrons, it can form a maximum of three covalent bonds. In boric acid, there are three –OH groups around the boron atoms.

Figure 2: Chemical Structure of Boric Acid

Boric acid is a weak acid. It is known as a Lewis acid because boron atom has empty orbitals that can be filled by incoming electrons. A Lewis acid is a compound or ionic species which can accept an electron pair from a donor compound. Boric acid form B[OH₄]^– when reacted with water; this is because of the binding of a –OH group from a water molecule, donating its electron pair to the empty orbital of the boron. Boric acid is a monobasic acid, meaning, it has only one replaceable hydrogen atom.

Boric acid can be produced by reacting borax with a mineral acid such as hydrochloric acid. The reaction for this process is given below.

Na₂B₄O₇·10H₂O + 2HCl → 4B(OH)₃ [or H₃BO₃] + 2NaCl + 5H₂O

Uses of Boric Acid

As an antiseptic
Fungicide
Flame retardant
Neutron absorber

Definition

Borax: Borax is a natural mineral having the chemical formula Na₂B₄O₇·10H₂O.

Boric Acid: Boric acid is a Lewis acid of boron having the chemical formula BH₃O₃.

IUPAC Name

Borax: The IUPAC name of borax is Sodium tetraborate decahydrate.

Boric Acid: The IUPAC name of boric acid is Trihydrooxidoboron.

Molar Mass

Borax: The molar mass of borax is 381.38 g/mol when hydrated and 201.22 g/mol when dehydrated.

Boric Acid: The molar mass of boric acid is 61.83 g/mol.

Melting Point and Boiling Point

Borax: The melting point of borax is 743 °C, and the boiling point is 1,575 °C.

Boric Acid: The melting point of boric acid is 170.9 °C, and the boiling point is 300 °C.

Nature

Borax: Borax is a naturally occurring mineral.

Boric Acid: Boric acid is a weak, monobasic Lewis acid.

Conclusion

Borax and boric acid are compounds of boron. Borax is a naturally occurring mineral. Boric acid can be obtained from borax via reaction with a mineral acid such as hydrochloric acid. Boric acid is a weak, monobasic Lewis acid. The main difference between borax and boric acid is that the chemical formula of borax is Na₂B₄O₇·10H₂O whereas the chemical formula of boric acid is BH₃O₃.

Reference:

1. Helmenstine, Anne Marie. “What Is Borax and Where Can You Get It?” ThoughtCo, Jul. 16, 2017, Available here.
2. “Borax.” Wikipedia, Wikimedia Foundation, 31 Dec. 2017, Available here.
3. “BORIC ACID.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.

Image Courtesy:

1. “Borax crystals” By Aram Dulyan (User:Aramgutang) – Own work (Public Domain) via Commons Wikimedia
2. “Boric-acid-2D” By Ben Mills – Own work (Public Domain) via Commons Wikimedia