Solved UPSC CDS/OTA Question
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Q · Soap and DetergentsMedium · 45s
Soaps are ineffective in hard water because:
TopicSoap and Detergents
Question Typemultiple choice
DifficultyMedium
Marking+1 / −0.33
Test Duration30 min
Step-by-Step Solution
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Soaps form insoluble calcium and magnesium salts (scum) with hard water ions, reducing cleansing power.
Final Answer: Option A — They react with Ca²⁺ and Mg²⁺ ions to form insoluble precipitates.