Assertion–Reason (Deliquescence of Common Salt):\nAssertion (A): When common salt is kept open, it absorbs moisture from the air.\nReason (R): Commercial common salt contains magnesium chloride (and similar impurities).

Introduction / Context:
The problem targets understanding of hygroscopic/deliquescent behavior in household salt. It tests whether moisture uptake is intrinsic to pure NaCl or due to impurities commonly present in table salt.

Given Data / Assumptions:

• Observation: “Common salt” kept open becomes moist.
• Claimed reason: Presence of magnesium chloride (and similar chlorides) in commercial salt.

Concept / Approach:
Pure sodium chloride is not strongly deliquescent at typical ambient conditions. However, impurities such as MgCl2 and CaCl2 are highly hygroscopic/deliquescent and readily absorb atmospheric moisture. In practice, commercial salts often contain traces of these chlorides, explaining the wetting effect. Conversely, “free-flow” table salts are treated with anti-caking agents to reduce clumping.

Step-by-Step Solution:
1) A: True—everyday experience and chemistry labs note moistening/clumping in open salt containers.2) R: True—MgCl2/CaCl2 absorb moisture; even small amounts can draw in water.3) Explanation: The impurities’ deliquescence directly causes the observed moisture uptake. Thus R explains A.

Verification / Alternative check:
Observe that very pure NaCl under controlled humidity clumps far less. Anti-caking additives (e.g., sodium ferrocyanide in tiny amounts) further mitigate moisture effects.

Why Other Options Are Wrong:
Any option denying R’s explanatory role conflicts with well-known hygroscopic behavior of alkaline earth chlorides.

Common Pitfalls:
Attributing the behavior solely to NaCl; ignoring role of impurities and ambient humidity.

Final Answer:
Both A and R are true, and R explains A.