Assertion (A) states that sodium metal is stored under kerosene. This is true because sodium is a highly reactive alkali metal that reacts vigorously with moisture and oxygen in the air. Storing it under kerosene (or mineral oil) prevents contact with air and water, thus preventing these reactions. Reason (R) states that metallic sodium melts when exposed to air. This is false. Sodium is a solid at room temperature and has a melting point of 97.8 °C. Exposure to air causes it to react and form compounds like sodium oxide or sodium hydroxide, but it does not cause it to melt.
Assertion (A): Sodium metal is stored under kerosene. Reason (R): Metallic sodium melts when exposed to air.
Asked in UPPCS Prelims 1998 · Topic: Metals, Minerals, Ores: Properties, Uses (Chemical properties of metals (reaction with oxygen, water, acids, bases, other metal salts))
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Answer: C. A is true, but R is false
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