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Question
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
Solution
P and Q
Lather (foam) is formed by the reaction of soap solution with sodium sulphate and potassium sulphate in the test tubes P and Q, respectively. They are dissolved in water to give a neutral solution.
Sulphates, chlorides and bicarbonates of calcium and magnesium make the water hard.
Thus, the lather is not formed in the test tubes R and S.
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RELATED QUESTIONS
List two problems that arise due to the use of detergents instead of soaps.
While preparing soap a small quantity of common salt is generally added to the reaction mixture of vegetable oil and sodium hydroxide. Which one of the following may be the purpose of adding common salt?
(A) To reduce the basic nature of the soap
(B) To make the soap neutral
(C) To enhance the cleansing power of the soap
(D) To favour the precipitation of the soap
In the neighbourhood of your school, hard water required for an experiment is not available. Select from the following group of salts available in your school, a group each member of which, if dissolved in distilled water, will make it hard:
(a) Sodium chloride, calcium chloride
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Hard water is not available for an experiment. Some salts are given below :
(I) Sodium chloride
(II) Sodium sulphate
(III) Calcium chloride
(IV) Calcium sulphate
(V) Potassium chloride
(VI) Magnesium sulphate
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(A) I, II, V
(B) I, III, V
(C) III, IV, VI
(D) II, IV, VI
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Fill in the following blank with suitable word:
The sodium salt of a long chain fatty acid is called .............
The chemical mostly used in the preparation of most of the soaps we use is
(a) Sodium chloride
(b) Potassium hydroxide
(c) Sodium hydroxide
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Water, coconut oil, and _______ are necessary for soap preparation.
In the soap micelles
What are soaps?
