Assertion–Reason (Deliquescence vs Hydrophobicity):\nAssertion (A): Common salt readily adsorbs moisture from the atmosphere.\nReason (R): Salts are hydrophobic.

Difficulty: Easy

Correct Answer: (A) is true, but (R) is false.

Explanation:


Introduction / Context:
This item distinguishes between hygroscopic/deliquescent behavior and hydrophobicity. It checks whether the stated reason matches the surface-chemistry phenomenon described in the assertion.


Given Data / Assumptions:

  • A: “Common salt” (typically NaCl; mixtures may include MgCl2, CaCl2, etc.) tends to pick up moisture in humid air.
  • R: “Salts are hydrophobic.”
  • Definitions: Hygroscopic substances attract water molecules; deliquescent substances absorb so much water that they dissolve. Hydrophobic substances repel water.


Concept / Approach:
Many ionic salts are hygroscopic or deliquescent, especially chlorides like CaCl2 and MgCl2. Table salt can cake in humid conditions due to impurities or accompanying anti-caking agents; the moisture affinity is hydrophilic, not hydrophobic.


Step-by-Step Solution:
1) A is substantially true in everyday observation: salt tends to clump by absorbing atmospheric moisture.2) R claims salts are hydrophobic. This is false: ionic solids are generally hydrophilic; some are strongly hygroscopic/deliquescent.3) Therefore the correct relationship is: A true, R false.


Verification / Alternative check:
Common desiccants include CaCl2 and silica gel; the former is a salt that actively absorbs moisture, confirming hydrophilicity.


Why Other Options Are Wrong:
(a)/(b) require R to be true; (d) inverts truth values; “None” is unnecessary.


Common Pitfalls:
Confusing “oily/hydrophobic” behavior with ionic solids; assuming NaCl itself is strongly deliquescent (it is mildly hygroscopic, but table salt caking often involves other salts/impurities).


Final Answer:
(A) is true, but (R) is false.

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