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JEE Main 2025 Apr 7 Shift 2, Chemistry Q8: Basic Concepts of Thermodynamic

JEE Main2025Apr 7, Shift 2Chemistry
Q.

The correct statement amongst the following is :

  1. A

    The term 'standard state' implies that the temperature is 0C

  2. B

    The standard state of pure gas is the pure gas at a pressure of 1 bar and temperature 273 K

  3. C

    is zero for O(g)

  4. D

    is zero for O(g)

Solution

The standard state of a substance is defined only by a fixed pressure of 1 bar; no particular temperature is fixed as part of the definition, so statements (1) and (2) are both incorrect since they wrongly tie standard state to a specific temperature.

The standard enthalpy of formation of an element in its most stable reference form is zero, but O(g) is not the stable form of oxygen; the stable reference form is O(g). Hence for O(g) is not zero, making statement (3) incorrect.

Since O(g) is the standard reference state of oxygen, its enthalpy of formation is zero at every temperature, including 500 K, so statement (4) is correct.

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