Washing Soda (Preparation) MCQs Quiz | Class 10
Test your understanding of Class X Science (Code 086), Unit I: Chemical Substances – Nature and Behaviour. This quiz covers the preparation of Washing Soda, including the Solvay process steps, thermal decomposition of baking soda, and recrystallization to form sodium carbonate decahydrate. Submit your answers to check your score and download the PDF solution.
Understanding Washing Soda Preparation
Washing soda is chemically known as Sodium Carbonate Decahydrate. Its chemical formula is Na2CO3.10H2O. It is an important basic salt used in various industries like glass, soap, and paper manufacturing, and for cleaning purposes.
Preparation Method
Washing soda is typically synthesized from sodium chloride (common salt) using the Solvay Process (Ammonia-Soda Process). The production involves three main stages:
- Formation of Baking Soda (Sodium Hydrogen Carbonate):
A cold and concentrated solution of sodium chloride (brine) is reacted with ammonia and carbon dioxide to form sodium hydrogen carbonate.
NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3 - Thermal Decomposition (Production of Soda Ash):
Sodium hydrogen carbonate is heated strongly. It decomposes to give anhydrous sodium carbonate (Soda Ash), water, and carbon dioxide.
2NaHCO3 (Heat) → Na2CO3 + H2O + CO2 - Recrystallization:
Anhydrous sodium carbonate is dissolved in water and recrystallized to obtain washing soda crystals containing 10 water molecules of crystallization.
Na2CO3 + 10H2O → Na2CO3.10H2O
Key Differences
| Compound | Formula | State |
|---|---|---|
| Soda Ash | Na2CO3 | Anhydrous (No water) |
| Washing Soda | Na2CO3.10H2O | Hydrated (10 H2O) |
Quick Revision Points
- Basic Nature: Washing soda is a salt of a strong base (NaOH) and a weak acid (H2CO3), so its aqueous solution is alkaline.
- Efflorescence: When exposed to air, washing soda loses 9 molecules of water to form a monohydrate.
- Hardness Removal: It is widely used to remove permanent hardness of water by forming insoluble carbonates with calcium and magnesium ions.
Extra Practice Questions
- Why is washing soda solution basic in nature?
- What happens when washing soda is heated strongly?
- Name the raw materials required for the Solvay process.
- Calculate the mass percentage of water in one molecule of washing soda.
- Write the reaction involved in the removal of permanent hardness of water using washing soda.
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