Washing soda softens hard water by removing which ions?
Answer and explanation
Correct answer: Calcium and magnesium ions
The hardness of water is mainly caused by dissolved calcium and magnesium ions, often present as bicarbonates, chlorides, or sulphates. Washing soda, Na₂CO₃·10H₂O, supplies carbonate ions that precipitate these ions as insoluble calcium carbonate and magnesium carbonate. Removing them softens the water, so option A is correct. Sodium and chloride ions generally do not cause ordinary hardness.
Frequently asked questions
What is the correct answer to this question?
Calcium and magnesium ions
Why is this the correct answer?
The hardness of water is mainly caused by dissolved calcium and magnesium ions, often present as bicarbonates, chlorides, or sulphates. Washing soda, Na₂CO₃·10H₂O, supplies carbonate ions that precipitate these ions as insoluble calcium carbonate and magnesium carbonate. Removing them softens the water, so option A is correct. Sodium and chloride ions generally do not cause ordinary hardness.
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.
