Why is sodium carbonate used to soften hard water?
Answer and explanation
Correct answer: It helps remove calcium and magnesium ions
Hard water contains dissolved calcium and magnesium ions, which react with soap and form scum. Sodium carbonate supplies carbonate ions that can precipitate these ions as insoluble carbonates, such as calcium carbonate. Removing or reducing these ions decreases hardness, so option A is correct. Sodium carbonate does not convert water into an acid, generate chlorine, or vaporise it; those statements do not describe water softening.
Frequently asked questions
What is the correct answer to this question?
It helps remove calcium and magnesium ions
Why is this the correct answer?
Hard water contains dissolved calcium and magnesium ions, which react with soap and form scum. Sodium carbonate supplies carbonate ions that can precipitate these ions as insoluble carbonates, such as calcium carbonate. Removing or reducing these ions decreases hardness, so option A is correct. Sodium carbonate does not convert water into an acid, generate chlorine, or vaporise it; those statements do not describe water softening.
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.
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