Explain the formation of scum when hard water is treated with soap.

AcademicChemistryNCERTClass 10

 Scum is formed when soap is used in hard water because a large amount of soap reacts with the magnesium and calcium ions of hard water producing an insoluble curdy precipitate that sticks to the clothes making them difficult to be cleaned.

[Extra information:Micelle formation takes place when soap is added to water. This is because when soap is added to water in which dirty clothes are soaked, the two parts of the soap molecule dissolve in two different mediums. The organic tail dissolves in the dirt, grime, or grease and the ionic head dissolves in water. When the clothes are rinsed or agitated, the dirt gets pulled out of the clothes in the water by the soap molecule. In this way, the soap does its cleaning work on dirty and grimy clothes or hands.
The soap molecules actually form a closed structure because of the mutual repulsion of the positively charged heads. This structure is called a micelle.]
Updated on 10-Oct-2022 12:47:19