Q. 94.5( 15 Votes )
The soap molecule has a
A. hydrophilic head and a hydrophobic tail
B. hydrophobic head and a hydrophilic tail
C. hydrophobic head and a hydrophobic tail
D. hydrophilic head and a hydrophilic tail
The soap molecule has a hydrophilic head and a hydrophobic tail. When soap is mixed into the water, the soap molecules arrange themselves into tiny clusters called 'micelles'. The hydrophilic parts of the soap (water-loving) molecules point outwards, forming the outer surface of the micelle. The hydrophobic parts (oil-loving) group together on the inner side. Micelles can trap fats in the center and helps to get rid of oil and dirt.
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Soaps are prepared by treating the esters of fatty acid with alkali. Sometimes common salt is also added to it. Why is common salt added during this process?All In One Science
Have you ever observed while cleaning cloth that foam is formed with difficulty and an insoluble substance (scum) remains after washing with water? This is caused by the reaction of soap with the calcium and magnesium salts, which cause the hardness of water. Hence, you need to use a larger amount of soap. This problem is overcome by using another class of compounds called detergents as cleansing agents. Detergents are generally ammonium or sulphonate salts of long chain carboxylic acids. The charged ends of these compounds do not form insoluble precipitates with the calcium and magnesium ions in hard water. Thus, they remain effective in hard water. Detergents are usually used to make shampoos and products for cleaning clothes.
(i) How will you test the hardness of water?
(ii) Why soap forms scum (insoluble substance) with hard water?
(iii) How one can overcome the problem of scum formation? What values do you identify in this context?All In One Science