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प्रश्न
Give a scientific explanation.
Soap forms a precipitate in hard water.
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उत्तर
When soap is mixed with hard water calcium and magnesium salts of fatty acids are formed. These being water insoluble they form a precipitate and that is why lather is not formed.
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संबंधित प्रश्न
Both soap and detergent are some type of salts. What is the difference between them?
Describe in brief the cleansing action of soap.
Why do soaps not form lather in hard water?
List two problems that arise due to the use of detergents instead of soaps.
In a locality, hard water, required for an experiment, is not available. However, the following salts are available in the school laboratory:
1. Sodium sulphate
2. Calcium sulphate
3. Magnesium chloride
4. Sodium chloride
5. Calcium chloride
6. Potassium sulphate
Which of the above salts may be dissolved in water to obtain hard water for the experiment?
(A) 2, 3 and 5
(B) 1, 2 and 5
(C) 1, 2, 4 and 6
(D) 3 and 5 only
People use a variety of methods to wash clothes. Usually after adding the soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?
State one use of saponification process.
Fill in the following blank with suitable word:
............. is better than soap for washing clothes when the water is hard.
What change will you observe if you test soap solution with a litmus paper (red and blue)? Give reason for your observation.
Why have detergents replaced soap as a washing agent?
Explain the cleansing action of soap. Draw diagrams to illustrate your answer.
The chemical which is not required for the preparation of soap in the laboratory is:
(a) vegetable oil
(b) baking soda
(c) caustic soda
(d) common salt
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
Give the reason of formation of scum when soaps are used with hard water.
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
Explain the action of soap in removing an oily spot from a piece of cloth.
Soap is a salt of ______ and sodium hydroxide.
Explain why synthetic detergents are superior to soap.
Arrange the following statements in correct sequence
- Pour that solution into an empty matchbox, soap can be obtained after drying.
- Take the necessary quantity of water in a jar.
- Then add coconut oil drop by drop and stir it well.
- Add concentrated sodium hydroxide in the jar and allow it to cool.
- Try this soap to wash your hand kerchief.
- Cover your work area with old newspaper.
How does soap clean clothes?
