What is the Chemical Formula of Borax with Structure Preparation Reactions and Uses
We have been using borax for cleaning purposes for ages. It was 1st traced in dry lake beds in Tibet and remained the only source of it till 1776 then Italy became the principal source of it until the 1860s. The famous 20-mule team borax company started in Death Valley, California, the US in 1889. It ruled the borax market for a long time.
What is Borax?
Borax is a natural mineral and a salt of boric acid. It is also known as sodium borate, sodium tetraborate, or disodium tetraborate. It is an important boron compound. Several closely related minerals that differ in their crystal water content such as decahydrate, pentahydrate, and octahydrate salts are also referred to as borax. Even its anhydrous form is also referred to as borax.
The formula of Borax – As we know the term borax is used for many closely related crystals. So, it has various formulas depending upon its water of crystallization.
Structure of Borax
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Properties of Borax
Physical Properties of Borax –
Its Molar Mass is 202.22 (anhydrous) and 381.38 (decahydrate).
It is a white-colored solid substance.
Its density is 2.4g/cm3 (anhydrous) and 1.73 g/cm3 (decahydrate).
Its melting point is 743 ℃ (anhydrous) and 75 ℃ (decahydrate).
It is soluble in water.
Its boiling point is 1,575℃ (anhydrous).
Chemical properties of Borax –
Borax reacts with acids and can be easily converted into boric acids which is a highly useful compound. The reaction is given below –
Na2B4O7·10H2O + 2HCl → 4B(OH)3 + 2NaCl + 5H2O
It is flammable and produces yellow-green flame.
It is very soluble in ethylene glycol and slightly soluble in acetone.
Reaction with sodium hydroxide –
Na2B4O7 + 7H2O + 2NaOH 🡪 4Na[B(OH)4]
Occurrence of Borax
Borax occurs naturally as deposits in seasonal lakes by their repeated evaporation. It is most commonly found in Turkey, Boron (California), Searles Lake, southwestern United States, the Atacama Desert in Chile, Bolivia, Tibet, and Romania, etc.
Uses of Borax
Few of the Uses of Borax are Listed Below –
As Cleaning Agent – Various properties of borax help to increase its cleaning power. It converts water into hydrogen peroxide during cleaning. It is highly basic so it makes the hot water basic which enhances the effectiveness of bleach or other cleaners.
As an Insect Killer – Borax stops the metabolic process of many organisms. This property of borax makes it a better disinfectant.
It is used in the test of diabetes mellitus.
It is used as a water softening agent.
For welding of iron and steel mixture of borax and ammonium chloride is used as a flux.
Boric Acid vs. Borax
Borax and Boric Acid are two boron chemicals that are related. Borax is a natural mineral that can be mined from the ground or collected from evaporating deposits. The refined chemical that arises from the processing of borax is boric acid (H3BO3). Borax is a boric acid salt. While the chemicals differ in several ways, both forms of the chemical will function for insect control and slime.
Where can I get Borax?
Borax can be found in laundry detergents, hand soaps, and some toothpaste. It is also in one of the following items:
Powdered hand soap
20 Mule Team Borax (pure borax)
Tooth bleaching formulations (check labels for borax or sodium tetraborate)
Some more uses of Borax
Borax has a lot of uses on its own, and it is included in a lot of other items. Here are a few examples of how borax powder and pure borax can be used in water:
Insecticide, used in roach-killing treatments and as a moth repellent (ten percent solution on wool)
Fungicide
Herbicide
Desiccant
Booster for laundry
Cleaner for the house
Agent for water softening
As a preservative, it is a food additive (banned in some countries)
Borax is used in a variety of other items, including:
Buffering solutions
Anti-flame agents
Bleaching toothpaste
Glass, ceramics, and pottery
Glazes made of enamel
This is a precursor to boric acid.
Green-colored flames, slime, and borax crystals are illustrations of science projects.
Chemistry of analysis bead test with borax
Welding flux for iron and steel
FAQs on Borax Formula Structure Properties and Chemical Behavior
1. What is the chemical formula of borax?
The chemical formula of borax is Na2B4O7·10H2O, which is sodium tetraborate decahydrate. This means each formula unit contains:
- 2 sodium ions (Na+)
- 1 tetraborate ion (B4O72−)
- 10 water molecules of crystallization (10H2O)
Borax is therefore a hydrated salt commonly used in chemistry laboratories and cleaning products.
2. What is the difference between borax and boric acid?
The main difference is that borax is Na2B4O7·10H2O (a salt), while boric acid is H3BO3 (a weak acid). Key differences include:
- Borax: Sodium salt of tetraborate, alkaline in solution.
- Boric acid: Weak Lewis acid of boron.
- Borax can form boric acid when treated with acid:
Na2B4O7(aq) + 2HCl(aq) + 5H2O(l) → 4H3BO3(aq) + 2NaCl(aq)
Both compounds contain boron but differ in chemical behavior and acidity.
3. Why is borax called sodium tetraborate decahydrate?
Borax is called sodium tetraborate decahydrate because its formula Na2B4O7·10H2O contains tetraborate ions and ten water molecules. The name breaks down as:
- Sodium → 2 Na+ ions
- Tetraborate → B4O72− ion (four boron atoms)
- Decahydrate → 10 molecules of water of crystallization
This naming follows standard inorganic nomenclature for hydrated salts.
4. What is the molar mass of borax?
The molar mass of borax (Na2B4O7·10H2O) is approximately 381.37 g/mol. It is calculated as:
- 2 Na = 2 × 22.99 = 45.98 g/mol
- 4 B = 4 × 10.81 = 43.24 g/mol
- 7 O = 7 × 16.00 = 112.00 g/mol
- 10 H2O = 10 × 18.02 = 180.20 g/mol
Total = 45.98 + 43.24 + 112.00 + 180.20 ≈ 381.37 g/mol.
5. Is borax an acid or a base?
Borax is a basic salt because it produces an alkaline solution in water. When dissolved, it undergoes hydrolysis:
B4O72−(aq) + 7H2O(l) ⇌ 4H3BO3(aq) + 2OH−(aq)
The formation of OH− ions makes the solution basic (pH ≈ 9–10).
6. What happens when borax is heated?
When borax is heated, it loses water of crystallization and forms anhydrous sodium tetraborate. The stepwise process includes:
- Removal of 10H2O on heating
Na2B4O7·10H2O(s) → Na2B4O7(s) + 10H2O(g)
Further strong heating produces a glassy mass known as borax bead, used in qualitative analysis.
7. What is the borax bead test in chemistry?
The borax bead test is a qualitative analysis method used to identify metal ions based on the color they produce in a borax glass bead. On heating, borax forms boron oxide:
Na2B4O7(s) → 2NaBO2(s) + B2O3(s)
- B2O3 dissolves metal oxides.
- Different metals give characteristic colors (e.g., Cu2+ → blue-green).
This test is commonly used in inorganic qualitative analysis.
8. How is borax prepared in the laboratory?
Borax is prepared by reacting boric acid with sodium carbonate, followed by crystallization. The balanced reaction is:
4H3BO3(aq) + Na2CO3(aq) → Na2B4O7(aq) + CO2(g) + 6H2O(l)
- The solution is concentrated.
- On cooling, crystals of Na2B4O7·10H2O separate out.
This method reflects the industrial preparation from boric acid.
9. What type of compound is borax?
Borax is an ionic hydrated salt composed of sodium ions and tetraborate ions with water of crystallization. Its structure includes:
- Na+ cations
- B4O72− complex anion
- 10 water molecules bound in the crystal lattice
Because of these water molecules, borax is classified as a decahydrate.
10. What are the common uses of borax in chemistry?
Borax is commonly used as a laboratory reagent, buffer component, and flux in metallurgy. Major uses include:
- Borax bead test for metal ion identification
- Preparation of boric acid (H3BO3)
- Component of buffer solutions
- Flux in welding and glass manufacturing
Its alkaline nature and ability to form glassy borates make it important in inorganic chemistry and industrial applications.
