A student takes four test tubes marked P, Q, R and S of 25 mL capacity and fills 10 mL of distilled water in each. He dissolves one spoon full of four different salts in each as − KCl in P, NaCl in Q, CaCl2 in R and MgCl2 in S. - Science


A student takes four test tubes marked P, Q, R and S of 25 mL capacity and fills 10 mL of distilled water in each. He dissolves one spoon full of four different salts in each as − KCl in P, NaCl in Q, CaCl2 in R and MgCl2 in S. He then adds about 2 mL of a sample of soap solution to each of the above test tubes. On shaking the contents of each of the test tubes, he is likely to observe a good amount of lather (foam) in the test tubes marked

(a) P and Q

(b) R and S

(c) P, Q and R

(d) P, Q and S



Scum is formed by the reaction of soap with calcium and magnesium salts in water. Test tubes R and S contain calcium chloride and magnesium chloride, respectively. Therefore, scum will be formed in these two tubes.

Test tubes P and Q contain potassium chloride and sodium chloride, respectively. Thus, a good amount of lather is likely to be formed in them.

Hence, the correct answer is option (a).

Concept: Soap
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2015-2016 (March) Delhi Set 1

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Differentiate between Toilet soap and Laundry soap.

Would you be able to check if water is hard by using a detergent?

What change will you observe if you test soap with litmus paper (red and blue)?

Mention the essential material (chemicals) to prepare soap in the laboratory. Describe in brief the test of determining the nature (acidic/alkaline) of the reaction mixture of saponification reaction. 

How is soap made? Write a word equation involved in soap making.


The soap molecule has a ______.

Which one of the following sets of materials can be used to prepare soap? 

(A) Neem oil and calcium hydroxide

(B) Castor oil and sodium hydroxide

(C) Mineral oil and sodium hydroxide

(D) Neem oil and magnesium hydroxide

A student takes 4 mL of distilled water in each of four test tubes I, II, III and IV, and then dissolves an equal amount of four different salts namely NaCl in I, CaCl2 in II, MgCl2 in III and KCl in IV. He then adds 8 drops of the given soap solution to each test tube and shakes the contents of the test tube 10 times. In which test tubes will enough lather (foam) be formed ?
(A) I and II
(B) II and III
(C) I and IV
(D) III and IV

Why are soaps not suitable for washing clothes when the water is hard?

Distinguish between esterification and saponification reactions of organic compounds.

Give a scientific explanation.

Soap forms a precipitate in hard water. 

Differentiate between:
Detergents and Soaps.

Fill appropriate term in the blank:

Soap is a salt of _______ and sodium hydroxide.

Write an answer to the following question.

How will you check with the help of soap powder whether water is hard?

Write an answer to the following question.

What is meant by 'surface activity'?

Write an answer to the following question.

Name three chemicals responsible for the surface activity of various detergents.

What are the differences between Soap and synthetic detergent?

What are the similarities and differences between Bath soap and soap for washing clothes?

Explain Why Soap cannot be used in hard water.

Explain Why Synthetic detergents are superior to soap.

Explain Why Often coloured spots are formed on clothes during washing.

The saponification of a fat or oil is done using _____ solution for hot process.

Water, coconut oil, and _______ are necessary for soap preparation.

Match the following

1. Soap C6H5 OH
2. Cement CaSO4.2H2O
3. Fertilizers NaOH
4. Gypsum RCC
5. Phenol NPK

Arrange the following statements in correct sequence

  1. Pour that solution into an empty matchbox, soap can be obtained after drying.
  2. Take the necessary quantity of water in a jar.
  3. Then add coconut oil drop by drop and stir it well.
  4. Add concentrated sodium hydroxide in the jar and allow it to cool.
  5. Try this soap to wash your hand kerchief.
  6. Cover your work area with old newspaper.

What are the three main constituents of soap?

What are the two different types of molecules found in the soap?

TFM in soaps represents ______ content in soap.

The alkaline hydrolysis of fatty acids is termed as ______


Used to join components: Adhesives:: Clean the body ______.

How does soap clean clothes?

______ to remove strong strains on the clothes.

______ are substances which can undergo chemical changes to produce certain materials.

What are soaps?

What are the similarities between Soap and synthetic detergent.


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