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प्रश्न
Why do soaps not work in hard water?
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उत्तर
Soaps are sodium or potassium salts of long-chain fatty acids. Hard water contains calcium and magnesium ions. When soaps are dissolved in hard water, these ions displace sodium or potassium from their salts and form insoluble calcium or magnesium salts of fatty acids. These insoluble salts separate as scum.
`2C_17H_35COONa + CaCl -> 2NaCl + (C_17H_35COO)_2Ca`
Soap Insiluable calcium Stearate(Soap)
This is the reason why soaps do not work in hard water.
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| Column I | Column II |
| (i) Soap chips | (a) dried miniature soap bubbles |
| (ii) Soap granules | (b) small broken pieces of soap formed from melted soaps |
| (iii) Soap powder | (c) soap powder + abrasives + builders \[\ce{(Na2CO3,Na3PO4)}\] |
| (iv) Scouring soap | (d) soap powder + builders like \[\ce{Na2CO3}\] and \[\ce{Na3PO4}\] |
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| Column I | Column II |
(i)  |
(a) Dishwashing powder |
(ii)  |
(b) Laundry soap |
| (iii) \[\ce{C17H33CO\overset{-}{O}\overset{+}{N}a + Na2CO3 + Rosin}\] | (c) Hair conditioners |
| (iv) \[\ce{CH3(CH2)16COO(CH2CH2O)nCH2CH2OH}\] | (d) Toothpaste |
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Reason: Ethanol makes things invisible.
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