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Question
Explain why soap cannot be used in hard water.
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Solution
Soaps cannot be used in hard water because they lose their cleansing property when used with it. Soaps do not form lather with hard water and instead form scum, as a result of which they lose their cleansing property.
RELATED QUESTIONS
A student takes about 4 ml of distilled water in four test tubes marked P, Q, R and S. He then dissolves in each test tube an equal amount of one salt in one test tube, namely sodium sulphate in P, potassium sulphate in Q, calcium sulphate in R and magnesium sulphate in S. After that he adds an equal amount of soap solution in each test tube. On shaking each of these test tubes well, he observes a good amount of lather (foam) in the test tube marked
(A) P and Q
(B) Q and R
(C) P, Q and S
(D) P, R and S
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Explain the formation of scum when hard water is treated with soap.
A student took four test tubes P, Q, R and S and filled about 8 mL of distilled water in each. After that he dissolved an equal amount of Na2SO4 in P, K2SO4 in Q, CaSO4 in R and MgSO4 in S. On adding an equal amount of soap solution and shaking each test tube well, a good amount of lather will be obtained in the test tubes:
(a) P and Q
(b) P and R
(c) P, Q and S
(d) Q, R and S
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(a) ionic ends directed towards the centre and hydrocarbon ends directed outwards
(b) hydrocarbon ends directed towards the centre and ionic ends directed outwards
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(d) both hydrocarbon ends and ionic ends directed outwards
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Why do soaps not work effectively in hard water?
