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JEE Main 2021 (31 Aug, Shift 1) · Gas Laws & Ideal Gas Equation

Gas Laws & Ideal Gas Equation question from JEE Main 2021 (31 Aug, Shift 1)

Q63JEE Main 2021 · 31 AUG · SHIFT 1Difficult

Gas Laws & Ideal Gas Equation

For an ideal gas the instantaneous change in pressure 'p' with volume 'v' is given by the equation dpdv=−ap\frac{dp}{dv} = -ap. If p = p0 at v =0 is the given boundary condition, then the maximum temperature one mole of gas can attain is: (Here R is the gas constant)

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Answer: (a)

  1. Integrate dpp=−a dv\frac{dp}{p} = -a\,dv with p=p0p = p_0 at v=0v = 0: p=p0e−avp = p_0 e^{-av}.
  2. For one mole T=pvR=p0ve−avRT = \frac{pv}{R} = \frac{p_0 v e^{-av}}{R}.
  3. dTdv=p0Re−av(1−av)=0⇒v=1a\frac{dT}{dv} = \frac{p_0}{R}e^{-av}(1 - av) = 0 \Rightarrow v = \frac{1}{a}.
  4. Tmax=p0R⋅1a⋅e−1=p0aeRT_{max} = \frac{p_0}{R}\cdot\frac{1}{a}\cdot e^{-1} = \frac{p_0}{aeR}
  5. So the answer is (a) p0aeR\frac{p_0}{aeR}.
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