Study Guides/Chemistry/Na2CO3 Chemical Name — Sodium Carbonate, Washing Soda, 106 g/mol
Study Guide · Chemistry

What Is the Chemical Name of Na2CO3?

Na2CO3 is the chemical formula for sodium carbonate. Its common name is washing soda (in the hydrated form Na2CO3·10H2O) or soda ash (in the anhydrous form). The molecular mass of Na2CO3 is 106 g/mol. It is a white, crystalline, water-soluble salt widely used in industrial processes, cleaning, and the glass industry.

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What is the chemical name of Na2CO3?

Answer

Na2CO3 is sodium carbonate. The anhydrous form is known as soda ash, and the hydrated form Na2CO3·10H2O is commonly called washing soda.

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Key Facts

Na2CO3 chemical name: sodium carbonate; common name: washing soda (hydrated form).

Molecular mass of Na2CO3 = 106 g/mol (2×23 + 12 + 3×16).

Hydrated form: Na2CO3·10H2O (washing soda), molecular mass = 286 g/mol.

Na2CO3 solution is alkaline (pH ~11.6) — turns red litmus blue.

Na2CO3·10H2O is efflorescent — loses water of crystallisation on exposure to dry air.

Used extensively in glass manufacturing, detergents, and water treatment.

Reacts with acids to produce CO2: Na2CO3 + 2HCl → 2NaCl + H2O + CO2.

Anhydrous Na2CO3 is called soda ash; monohydrate is called crystal carbonate.

Chemical Name and Formula of Na2CO3

Na2CO3 is the chemical formula for sodium carbonate. It contains two sodium (Na) atoms, one carbon (C) atom, and three oxygen (O) atoms. Common names include:

  • Anhydrous form (Na2CO3): Soda ash
  • Decahydrate form (Na2CO3·10H2O): Washing soda
  • Monohydrate form (Na2CO3·H2O): Crystal carbonate

Sodium carbonate is a salt of a strong base (NaOH) and a weak acid (H2CO3), making its aqueous solution alkaline (basic). Its solutions turn red litmus paper blue.

Molecular Mass Calculation

The molecular mass of Na2CO3 is calculated as follows:

Na2CO3: 2 × Na + 1 × C + 3 × O = 2 × 23 + 12 + 3 × 16 = 46 + 12 + 48 = 106 g/mol

For the decahydrate (washing soda), Na2CO3·10H2O: = 106 + 10 × 18 = 106 + 180 = 286 g/mol

Atomic masses: Na = 23, C = 12, O = 16, H = 1.

Physical Properties of Sodium Carbonate

Physical properties of Na2CO3:

  • Appearance: White crystalline powder (anhydrous); colourless crystals (decahydrate)
  • Odour: Odourless
  • Taste: Strongly alkaline
  • Melting point: 851°C (anhydrous)
  • Solubility: Highly soluble in water (~215 g/L at 20°C)
  • Aqueous solution pH: ~11.6 (alkaline)
  • Density: 2.54 g/cm³ (anhydrous)

Efflorescence: Na2CO3·10H2O loses water of crystallisation on exposure to air, converting to the monohydrate or anhydrous form — a process called efflorescence.

Chemical Properties and Reactions

Key chemical reactions of Na2CO3:

  1. Reaction with acids (neutralisation): Na2CO3 + H2SO4 → Na2SO4 + H2O + CO2 Na2CO3 + 2HCl → 2NaCl + H2O + CO2

  2. Reaction with calcium hydroxide (Solvay process-related): Na2CO3 + Ca(OH)2 → 2NaOH + CaCO3↓

  3. Hydrolysis in water (alkaline reaction): CO3²⁻ + H2O ⇌ HCO3⁻ + OH⁻ (This is why Na2CO3 solution is alkaline)

  4. Heating: Na2CO3 is thermally stable and does not decompose easily, unlike NaHCO3.

Uses of Sodium Carbonate (Na2CO3)

Na2CO3 has extensive industrial and domestic uses:

  1. Glass manufacturing: One of the main raw materials for making glass (along with SiO2 and CaCO3).
  2. Detergents and cleaning: Washing soda (Na2CO3·10H2O) softens hard water by precipitating Ca²⁺ and Mg²⁺ ions.
  3. Paper industry: Used in the Kraft process for wood pulp treatment.
  4. Textile industry: Used in dyeing and bleaching.
  5. Water treatment: Adjusts the pH of water.
  6. Food industry: Used as a food additive (E500) to regulate acidity.
  7. Laboratory reagent: Used as a primary standard in titrimetric analysis.

Questions and Answers

What is the chemical name of Na2CO3?+

Na2CO3 is sodium carbonate. The anhydrous form is known as soda ash, and the hydrated form Na2CO3·10H2O is commonly called washing soda.

What is the molecular mass of Na2CO3?+

The molecular mass of Na2CO3 is 106 g/mol. Calculation: 2×23 (Na) + 12 (C) + 3×16 (O) = 46 + 12 + 48 = 106 g/mol.

Why is Na2CO3 solution alkaline?+

Na2CO3 is a salt of strong base (NaOH) and weak acid (H2CO3). In water, carbonate ion hydrolyses: CO3²⁻ + H2O ⇌ HCO3⁻ + OH⁻, releasing OH⁻ ions and making the solution alkaline (pH ~11.6).

What is the difference between NaHCO3 and Na2CO3?+

NaHCO3 (sodium bicarbonate / baking soda) has one sodium and one hydrogen in the formula, with molecular mass 84 g/mol. Na2CO3 (sodium carbonate / washing soda) has two sodium atoms and molecular mass 106 g/mol. Na2CO3 is more alkaline and thermally more stable than NaHCO3.

What is washing soda used for?+

Washing soda (Na2CO3·10H2O) is used to soften hard water (by precipitating Ca²⁺ and Mg²⁺), as a cleaning agent in laundry, in glass manufacturing, paper production, and as a laboratory reagent.

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