Which substance is used to soften hard water?
Answer and explanation
Correct answer: Washing soda
Hard water contains dissolved calcium and magnesium ions, which interfere with soap and form scum. Washing soda, sodium carbonate (Na₂CO₃), reacts with these ions and precipitates them as insoluble carbonates, thereby removing their effect and softening the water. Baking powder, vinegar, and sugar do not provide this water-softening action in the stated context, so option A is correct.
Frequently asked questions
What is the correct answer to this question?
Washing soda
Why is this the correct answer?
Hard water contains dissolved calcium and magnesium ions, which interfere with soap and form scum. Washing soda, sodium carbonate (Na₂CO₃), reacts with these ions and precipitates them as insoluble carbonates, thereby removing their effect and softening the water. Baking powder, vinegar, and sugar do not provide this water-softening action in the stated context, so option A is correct.
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.
