Soap does not work properly when water is hard. This is primarily because hard water contains salts of calcium and magnesium. When soap is added to hard water, it reacts with these salts to form an insoluble substance called scum. A lot of soap is wasted in the process. In addition, soaps do not give lather with hard water. When formed, the scum sticks to the cloth and decreases the cleansing ability of the soap.
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This problem is overcome by using detergents.
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Explain this para pls...............
Answers
When soap molecules are present in water, the molecules arrange themselves in the form of a cluster in such a manner that their hydrophobic ends are away from the water molecules and their hydrophilic or ionic ends are towards the water molecules, as shown in the figure. This is known as micelle formations.
Cleaning action of soaps:
The dirt (oil and grease) present on clothes is organic in nature, and insoluble in water. Hence, it cannot be removed only by washing with water. When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth, as shown sequentially in the following figure.Cleansing
Then, the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster. These micelles remain suspended in water like particles in a colloidal solution. The various micelles present in water do not come together to form a precipitate as each micelle repels the others because of ion-ion repulsion. Thus, the dust particles remain trapped in the micelles (which remain suspended), and are easily rinsed away by water. Hence, soap micelles remove the dirt by dissolving it in water.