Q. 50 B4.2( 13 Votes )
What is saponification? Write the reaction involved in this process.
Soaps are made by the process of saponification. Soaps are sodium or potassium salts of long chain fatty acids. When triglycerides in fats react with aqueous NaOH or KOH, they are converted into soap and glycerol. This is called saponification or alkaline hydrolysis of esters.
CH2COOC2H5 + NaOH → CH3 COONa + C2H5OH
The soap molecule has two parts: a polar group (-COO-Na+) and a non-polar group (R-hydrocarbon part). The polar group is called the head and the non-polar group is called the tail. Therefore, the soap molecule has a polar head and a non-polar hydrocarbon tail. The polar head is water loving in nature (hydrophilic) and the non-polar tail is water repelling (hydrophobic) in nature.
The saponification reaction is exothermic in nature.
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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