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JEE Main 2026 (23 Jan, Shift 2) · Thermodynamic Processes

Thermodynamic Processes question from JEE Main 2026 (23 Jan, Shift 2)

Q43JEE Main 2026 · 23 JAN · SHIFT 2Medium

Thermodynamic Processes

One mole of an ideal diatomic gas expands from volume VV to 2V2V isothermally at a temperature 27∘C27^\circ\text{C} and does WW joule of work. If the gas undergoes same magnitude of expansion adiabatically from 27∘C27^\circ\text{C} doing the same amount of work WW, then its final temperature will be (close to) ‾ ∘C. (log⁡e2=0.693)\underline{\hspace{3em}}\ ^\circ\text{C}.\ (\log_e 2 = 0.693)

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Answer: (a)

  1. Isothermal work: W=nRTln⁡2=1×8.314×300×0.693≈1728W = nRT\ln 2 = 1 \times 8.314 \times 300 \times 0.693 \approx 1728 J.
  2. Adiabatic work: W=nCv(T1−T2)W = nC_v(T_1 - T_2) with Cv=52R=20.8C_v = \frac{5}{2}R = 20.8 J mol−1^{-1} K−1^{-1}.
  3. T1−T2=172820.8≈83T_1 - T_2 = \frac{1728}{20.8} \approx 83 K
  4. T2≈27−83=−56∘T_2 \approx 27 - 83 = -56^\circC
  5. So the answer is (a) −56-56.
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