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प्रश्न
Explain the formation of scum when hard water is treated with soap.
उत्तर १
Hard water often contains salts of calcium and magnesium. Soap molecules react with calcium and magnesium salts and form a precipitate. This precipitate begins floating as an off-white layer over water. This layer is called scum. Soaps lose their cleansing property in hard water because of formation of scum.
\[\ce{\underset{Hard water}{Ca^{2+}} + \underset{Soap}{2RCOONa} -> \underset{Cal. salt (ppt{.})}{(RCOO)2Ca} + 2Na+}\]
\[\ce{\underset{Hard water}{Mg^{2+}} + \underset{Soap}{2RCOONa} -> \underset{Mag. salt (ppt{.})}{(RCOO)2Mg} + 2Na+}\]
उत्तर २
Scum is formed when a soap is used in hard water. This happens because a large amount of soap is utilised in reacting with the magnesium and calcium ions of hard water. An insoluble curdy precipitate, scum, sticks to the clothes making them difficult to be cleaned.
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संबंधित प्रश्न
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
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
Select from the following group of these salts, each member of which may be dissolved in water to make it hard.
(A) I, II, V
(B) I, III, V
(C) III, IV, VI
(D) II, IV, VI
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.
What are the raw materials required for making soap in a laboratory (or at home)?
What is a detergent? Name one detergent.
What is saponification? Write the chemical equation of the reaction involved in this process. Name all the substances which take part in this process and also those which are formed.
In a soap micelle, the soap molecules are arranged radially with:
(a) ionic ends directed towards the centre and hydrocarbon ends directed outwards
(b) hydrocarbon ends directed towards the centre and ionic ends directed outwards
(c) both ionic ends and hydrocarbon ends directed toward the centre
(d) both hydrocarbon ends and ionic ends directed outwards
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
A student is testing water to know which is best for cleansing purposes with soaps. He would find that the cleansing action of soaps is best when he uses water obtained from
(a) rain
(b) tap
(c) hand pump
(d) pond
Soap is a salt of ______ and sodium hydroxide.
How will you check with the help of soap powder whether water is hard?
What are the differences between Soap and synthetic detergent?
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
- 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.
What are the two different types of molecules found in the soap?
Soaps are ester of which type of acids?
In the soap micelles
- Write the formula and draw electron dot structure of carbon tetrachloride.
- What is saponification? Write the reaction involved in this process.
