Assertion (A): Detergents are more effective than soaps in hard water. Reason (R): Detergents do not form insoluble precipitates with calcium and magnesium ions. MCQ with Answer and Explanation
Assertion (A): Detergents are more effective than soaps in hard water. Reason (R): Detergents do not form insoluble precipitates with calcium and magnesium ions.
A. Both A and R are true and R is the correct explanation of A.
B. A is false but R is true.
C. Both A and R are true but R is NOT the correct explanation of A.
D. A is true but R is false.
Answer: Option A
Solution (By JKSSB Mock Tests)
Soaps react with Ca²⁺ and Mg²⁺ ions in hard water to form insoluble scum (calcium/magnesium stearate), wasting soap and reducing cleaning efficiency. Detergents form soluble salts with these ions, so they lather well and clean effectively in hard water. Both statements are correct and R explains A.
Explanation:
Salt is obtained by evaporation of seawater in shallow ponds. Water evaporates leaving salt behind. Filtration cannot separate dissolved salt. Distillation would give pure water, not salt. Sublimation for sublimable solids.
Explanation:
Aqua regia (royal water) is a 3:1 mixture by volume of concentrated HCl and HNO₃. It generates nascent chlorine and nitrosyl chloride, which oxidize gold and platinum to soluble chloro complexes (e.g., HAuCl₄). Neither acid alone can dissolve these noble metals. Used for cleaning glassware and in etching. Must be prepared fresh and handled with extreme care.
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