Washing soda helps soften hard water by removing which ions?
Answer and explanation
Correct answer: Calcium and magnesium ions
Hard water mainly contains dissolved calcium ions, Ca²⁺, and magnesium ions, Mg²⁺, which react with soap to form scum. Washing soda, sodium carbonate, supplies carbonate ions that precipitate these ions as insoluble carbonates, such as calcium carbonate and magnesium carbonate. Removing them reduces water hardness, so option A is correct. Sodium and chloride ions generally remain soluble and 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?
Hard water mainly contains dissolved calcium ions, Ca²⁺, and magnesium ions, Mg²⁺, which react with soap to form scum. Washing soda, sodium carbonate, supplies carbonate ions that precipitate these ions as insoluble carbonates, such as calcium carbonate and magnesium carbonate. Removing them reduces water hardness, so option A is correct. Sodium and chloride ions generally remain soluble and 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.
