JEE Main & Advanced Sample Paper JEE Main Sample Paper-22

  • question_answer
    AT \[{{27}^{o}}C\] the volume of a monoatomic ideal gas is V. The gas is expanded to 2V by adiabatic process.  Find (i) final temperature of gas and (ii) change in internal energy [R=8.31J/mol-K]

    A)  189 K & + 2700.23 J

    B)  100 K & + 2500J

    C)  100 K & - 2000,23J

    D)  189 K & -  2767.23 J

    Correct Answer: D

    Solution :

    (i) In adiabatic process, \[{{T}_{1}}V_{1}^{\gamma -1}\,={{T}_{2}}V_{2}^{\gamma -1}\,\] and here\[\gamma =5/3\] \[\therefore \,\,300\,\times \,{{V}^{2/3}}\,=T{{(2V)}^{2/3}}\] \[T=300/{{(2)}^{2/3}}\,=189K\] (ii) \[dU=\frac{nRdT}{(\gamma -1)}\,[dU\,=n{{C}_{v}}dT\] and \[{{C}_{v}}=\frac{R}{\gamma -1}\,\]] \[\therefore \,\,dU=2\,\times 3/2\,\times 8.31\,(189-300\,)=2767.23J\]


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