How does washing soda help in softening hard water?
Answer and explanation
Correct answer: By precipitating calcium and magnesium ions
The governing concept is the removal of hardness-causing ions. Hard water contains dissolved calcium and magnesium salts. 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, leaving softer water. Therefore, option A is correct; the other options do not describe the chemical process of softening.
Frequently asked questions
What is the correct answer to this question?
By precipitating calcium and magnesium ions
Why is this the correct answer?
The governing concept is the removal of hardness-causing ions. Hard water contains dissolved calcium and magnesium salts. 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, leaving softer water. Therefore, option A is correct; the other options do not describe the chemical process of 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.
