JEE Main levelSingle correct optionDifficulty 2 of 3el182
Assertion (A): Synthetic detergents can be used for washing in hard water.
Reason (R): The calcium and magnesium salts of alkyl sulphates and alkylbenzenesulphonates are water soluble, so no scum is formed.
ABoth A and R are true, and R is the correct explanation of A
BBoth A and R are true, but R is not the correct explanation of A
CA is true but R is false
DA is false but R is true
Answer: A
Detergents such as CX12HX25OSOX3Na do not leave an insoluble scum with CaX2+ and MgX2+ (standard NCERT treatment), so they keep lathering in hard water. R is true and is exactly why A holds.