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NEET CHEMISTRYThermodynamicsMedium

Question

If for a given substance melting point is TBT_B and freezing point is TAT_A, then correct variation shown by graph between entropy change and temperature is

A

Graph 1

B

Graph 2

C

Graph 3

D

Graph 4

Step-by-Step Solution

For a pure substance, the melting point (TBT_B) and freezing point (TAT_A) are the same, i.e., TA=TBT_A = T_B. As the temperature increases, the entropy of the substance also increases. At the melting point, the substance undergoes a phase transition from solid to liquid. During this process, heat is absorbed at a constant temperature, leading to a sudden and discontinuous increase in entropy (since the liquid state is more disordered than the solid state). After the melting is complete, the entropy of the liquid continues to increase with temperature. The correct graph would show a steady increase, a vertical jump in entropy at TA=TBT_A = T_B, and then a continued increase.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Thermodynamics. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYThermodynamicssubstancemeltingfreezingcorrectvariation

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