Science
(i) With the help of a diagram, show the formation of micelles, when soap is applied on oily dirt.
(ii) Take two test tubes X and Y with 10 mL of hard water in each.
In test tube 'X', add few drops of soap solution and in test tube 'Y' add a few drops of detergent solution. Shake both the test tubes for the same period.
(1) In which test tube the formation of foam will be more ? Why ?
(2) In which test tube is a curdy solid formed ? Why ?
Answer
(i) Diagram showing the formation of micelles when soap is applied on oily dirt is given below:
(ii) The test tube containing detergents (i.e. Y) will form more foam because detergents are generally ammonium or sulphonate salts of long carboxylic acids. The charged ends of these compounds do not form insoluble precipitates with the calcium and magnesium ions in hard water. Hence, detergents remain effective even in hard water.
(iii) The test tube containing soap (i.e. X) will show a curdy white precipitate because soap molecules react with calcium and magnesium salts of hard water and form the floating off-white layer over water called as scum.
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