Page 3 - 3.LESSON NOTES-(CH-2 WASHING SODA& PLASTER OF PARIS)

• Hard And Soft water. ..

. Soft water: Water that produces lather with soap readily is called soft water.
For ex: Rain water ,distilled water ,demineralised water

Hard water: Water which does not produce lather with soap readily is called hard
water.
Hard water... is that water which contains an appreciable quantity of dissolved
minerals (like calcium and magnesium salts of
Bicarbonates/Chlorides/Sulphates)

For ex: Tube well water & Open well water ,.

• Signs of hard water in your home include:

1. White scaling on faucets.
2. Soap scum on tubs and sinks.
3. Dingy whites from your laundry.
4. Mineral residue left on dishes and glassware.
Temporary Hard water consists of – Ca(HCO3)2 or Mg(HCO3)2
Permanent Hard Water may contain Chlorides of Ca/Mg – CaCl2 or MgCl2,
OR Sulphates of Ca/Mg – CaSO4 or MgSO4

Washing soda reacts with hard water to form insoluble ppt of Ca & Mg such
that they get separated from the hard water, making it soft:

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