How does washing soda work in softening hard water?
Answer and explanation
Correct answer: It removes calcium and magnesium ions as insoluble carbonates
Hard water contains dissolved calcium and magnesium ions. Washing soda supplies carbonate ions, which react with them to form sparingly soluble calcium carbonate and magnesium carbonate precipitates. Removing these ions reduces hardness and allows soap to lather more readily. Therefore option A is correct; the other choices describe unrelated changes that do not soften water.
Frequently asked questions
What is the correct answer to this question?
It removes calcium and magnesium ions as insoluble carbonates
Why is this the correct answer?
Hard water contains dissolved calcium and magnesium ions. Washing soda supplies carbonate ions, which react with them to form sparingly soluble calcium carbonate and magnesium carbonate precipitates. Removing these ions reduces hardness and allows soap to lather more readily. Therefore option A is correct; the other choices describe unrelated changes that do not soften 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.
