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NCERT Class XII Chemistry
Chapter - Chemistry in Everyday Life
Questions with Solutions

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Question : 23
Total: 32
Why do soaps not work in hard water?
Solution:  
Hard water contains calcium and magnesium ions. These ions form insoluble calcium and magnesium soaps respectively when sodium or potassium soaps are dissolved in hard water.
2C17H35COONa+CaCl2→2NaCl+(C17H35COO)2Ca
soap‌‌‌‌‌Insoluble‌Calcium‌Stearate(Soap)
These insoluble soaps separate as scum in water and are useless as cleansing agent. In fact these are hindrance to good washing, because the precipitate adheres onto the fibre of the cloth as gummy mass.
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