Sodium carbonate (commonly known as washing soda, soda ash, or soda crystals) is an inorganic chemical having the formula Na₂CO₃ and different hydrates. All forms are white, odourless, and water-soluble salts that produce alkaline solutions in water. Historically, it has originated from the ashes of plants cultivated in sodium-rich soils, and because the ashes of these sodium-rich plants differed significantly from wood ashes (before used to generate potash), sodium carbonate became known as "soda ash." Sodium carbonate is produced in large quantities through the Solvay process, using sodium chloride and limestone as raw materials. It is also manufactured by carbonating sodium hydroxide, which is obtained via the chloralkali process.
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Maharashtra State Board: Class 9
Introduction:
Maharashtra State Board: Class 9
Experiment
1. Aim: To observe the effect of washing soda on the hardness of water and the lather formation with soap.
2. Requirements: water sample from a well or borewell, beaker, soap, and washing soda (Na₂CO₃).
3. Procedure:
- Take a sample of hard water in a beaker.
- Add some soap to the water and stir. Observe the lather formation.
- In another sample of the same water, add one spoonful of washing soda and stir.
- Add soap to this treated water and stir again. Observe the changes in lather formation.
4. Observation: Hard water initially produces little to no lather with soap. After adding washing soda, the water becomes soft, and lather formation with soap increases.
5. Conclusion: The hardness of water is caused by the presence of calcium and magnesium salts (chlorides and sulphates). Washing soda (Na₂CO₃) reacts with these salts, forming insoluble carbonates of calcium and magnesium, which are removed. This softens the water, allowing soap to form lather effectively.
MgCl₂ (aq) + Na₂CO₃ (s) → MgCO₃ (s) + 2 NaCl (s)
Sodium carbonate is a water-soluble salt of sodium. Crystalline sodium carbonate, on keeping, loses its water of crystallisation readily, and a white powder is obtained. This powder is called washing soda.
$\mathrm{Na_{2}CO_{3}.10~H_{2}O}\xrightarrow{-H_{2}O}\mathrm{Na_{2}CO_{3}.H_{2}O}$
Maharashtra State Board: Class 9
Properties:
- Washing soda is a white, odourless powder at room temperature.
- Its aqueous solution turns litmus paper blue, indicating its alkaline nature.
- It is hygroscopic, meaning it absorbs moisture from the air when exposed.
- Composed of hydrated sodium carbonate (Na₂CO₃·10H₂O), it loses water of crystallisation upon heating.
- Easily dissolves in water, forming an alkaline solution.
- Acts as a mild alkali, useful in various chemical reactions.
- Non-toxic and safe for household and industrial applications.
Maharashtra State Board: Class 9
