Washing soda softens hard water. Removal of which ions gives this effect?
Answer and explanation
Correct answer: Calcium and magnesium ions
Hardness of water is mainly caused by dissolved calcium ions (Ca²⁺) and magnesium ions (Mg²⁺). Washing soda, sodium carbonate (Na₂CO₃), reacts with these ions and forms insoluble carbonates such as calcium carbonate and magnesium carbonate. These precipitates can be separated, so the hardness-producing ions are removed. The other options do not represent the ions responsible for ordinary hard water.
Frequently asked questions
What is the correct answer to this question?
Calcium and magnesium ions
Why is this the correct answer?
Hardness of water is mainly caused by dissolved calcium ions (Ca²⁺) and magnesium ions (Mg²⁺). Washing soda, sodium carbonate (Na₂CO₃), reacts with these ions and forms insoluble carbonates such as calcium carbonate and magnesium carbonate. These precipitates can be separated, so the hardness-producing ions are removed. The other options do not represent the ions responsible for ordinary hard water.
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.
