Which salt is used for washing clothes and for removing the permanent hardness of hard water?
Answer and explanation
Correct answer: Na₂CO₃·10H₂O / Sodium carbonate decahydrate
Na₂CO₃·10H₂O is washing soda, or sodium carbonate decahydrate. Its carbonate ions react with dissolved Ca²⁺ and Mg²⁺ ions responsible for permanent hardness, producing insoluble carbonates that can be removed. NaHCO₃ is baking soda, CaOCl₂ is bleaching powder, and CaSO₄·½H₂O is plaster of Paris. Therefore, the salt used for washing and softening hard water is option A.
Frequently asked questions
What is the correct answer to this question?
Na₂CO₃·10H₂O / Sodium carbonate decahydrate
Why is this the correct answer?
Na₂CO₃·10H₂O is washing soda, or sodium carbonate decahydrate. Its carbonate ions react with dissolved Ca²⁺ and Mg²⁺ ions responsible for permanent hardness, producing insoluble carbonates that can be removed. NaHCO₃ is baking soda, CaOCl₂ is bleaching powder, and CaSO₄·½H₂O is plaster of Paris. Therefore, the salt used for washing and softening hard water is option A.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
