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Hard Water

Sunita perfor...

Question

Sunita performs two sets of experiments to study the formation of lather(foam) by using liquid soap.
Set 1 : She takes 10 ml of distilled water in test tube 'A', adds 5-6 drops of liquid soap in it and shakes the test tube vigorously.
Set 2 : She takes 10 ml of distilled water in test tube 'B', adds 5-6 drops of liquid soap in it alongwith half spoonful of CaSO₄, and shakes the test tube vigorously.
(a) In which test tube, A or B, less lather is formed? Why?
(b) In which test tube, A or B, more lather is formed? Why?

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Solution

(a) Test tube "B" has less lather due to the presence of calcium ions. Due to the presence of calcium ions water become hard and in hard water, lather formation decreases.

(b) Test tube "A" has more lather because it is soft water. In soft water, lather formation increases and cleansing action increases.

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