Q. 204.0( 6 Votes )
How would you predict whether a given water sample is of hard water or soft water? Give chemical equation.
To determine whether a given water sample is of hard water or soft water, one can use soap.
Soap produces lather in soft water whereas soap does not produce lather in hard water due to the formation of scum (insoluble precipitate). Scum is a result of reaction of soap with calcium and magnesium ions present in the hard water.
Rate this question :
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