HARD WATER
CLASS 9 & 10 · CHEMISTRY
Soap in Soft vs Hard Water
soft water
hard water
Mg²⁺
Ca²⁺
Mg²⁺
Ca²⁺
Mg²⁺
Ca²⁺
lots of lather ✔
scum, little lather ✗
Boil it or add washing soda
removes Ca²⁺ / Mg²⁺ → soft water
STEP 1
prostudypk.com · free MCQ tests
REMEMBER
Ca²⁺ + Mg²⁺ = hard
Hard water wastes soap and forms scum
Temporary hardness: removed by boiling
Permanent: use washing soda (Na₂CO₃)
Free test → prostudypk.com
CLASS 9 & 10 · CHEMISTRY
Why won't soap lather in some tap water?
Hard water in 25 seconds
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