Advertisements
Advertisements
प्रश्न
Answer the following question.
In three test tubes A, B, and C, three different liquids namely, distilled water, underground water and distilled water in which a pinch of calcium sulphate is dissolved, respectively are taken. Equal amount of soap Answer is added to each test tube and the contents are shaken. In which test tube will the length of the foam (lather) be longest? Justify your answer.
उत्तर
Test tube A contains distilled water which is considered as soft water, free from ions like Mg2÷, Ca2+, etc. So, in this case, the length of foam will be the longest(maximum). Test tube B contains underground water which contains ions like Mg2+, Ca2÷, etc. which react with soaps to form salts of fatty acids called scum, which is insoluble in water. So, in this case, the length of foam will be less in comparison to test tube A. Test tube C contains distilled water with CaSO4, which contains Ca2÷ ions which react with soaps to form salts of fatty acids called scum, which is insoluble in water. So, in this case, also, the length of foam will be less in comparison to test tube A.
APPEARS IN
संबंधित प्रश्न
Why do soaps not form lather in hard water?
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
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
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.
Give any two differences between soaps and detergents.
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.
Why are soaps not suitable for washing clothes when the water is hard?
Write an answer to the following question.
Name three chemicals responsible for the surface activity of various detergents.
Explain why synthetic detergents are superior to soap.
