Medium MCQ +4 / -1 PYQ · JEE Mains 2021

One mole of an ideal gas is taken through an adiabatic process where the temperature rises from 27$^\circ$ C to 37$^\circ$ C. If the ideal gas is composed of polyatomic molecule that has 4 vibrational modes, which of the following is true? [R = 8.314 J mol$-$1 k$-$1]

  1. A work done by the gas is close to 332 J
  2. B work done on the gas is close to 582 J Correct answer
  3. C work done by the gas is close to 582 J
  4. D work done on the gas is close to 332 J

Solution

Since, each vibrational mode, corresponds to two degrees of freedom, hence, f = 3 (trans.) + 3 (rot.) + 4 $\times$ 2 (vib.) = 14<br><br> &amp; $\gamma = 1 + {2 \over f}$<br><br>$\gamma = 1 + {2 \over {14}} = {8 \over 7}$<br><br>$W = {{nR\Delta T} \over {\gamma - 1}} = - 582$<br><br>As W &lt; 0. work is done on the gas.

About this question

Subject: Physics · Chapter: Thermodynamics · Topic: Zeroth and First Law

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