Multiple choice

Washing soda is used with soap to _______ the water for washing clothes.

  1. harden

  2. increase

  3. clean

  4. soften
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Washing soda (sodium carbonate decahydrate, Na2CO3·10H2O) is a water softener. It reacts with calcium and magnesium ions in hard water, converting them into soluble forms, thus softening the water. Softened water allows soap to lather better and clean clothes more effectively. Hard water reduces soap's cleaning efficiency.

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