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NEET CHEMISTRYThermodynamicsEasy

Question

The work done to contract a gas in a cylinder is 462 joules. 128 joule energy is evolved in the process. What will be the internal energy change in the process? [MP PMT 2003]

A
  • 590 joules
B

– 334 joules

C
  • 334 joules
D

– 590 joules

Step-by-Step Solution

To determine the change in internal energy (ΔU\Delta U), we apply the First Law of Thermodynamics, which is mathematically expressed as ΔU=q+w\Delta U = q + w .

  1. Work (ww): According to the IUPAC sign convention used in thermodynamics, work done on the system (such as during compression or contraction) is assigned a positive sign . Therefore, w=+462w = +462 J.
  2. Heat (qq): Heat evolved (released) by the system to the surroundings is assigned a negative sign . Therefore, q=128q = -128 J.
  3. Calculation: Substituting these values into the first law equation: ΔU=(128 J)+(+462 J)=+334 J\Delta U = (-128\text{ J}) + (+462\text{ J}) = +334\text{ J}.

The internal energy of the system increases by 334 joules, which matches Option C.

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.

CHEMISTRYThermodynamicscontractcylinderjoulesenergyevolved

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