NEET Sample Paper NEET Sample Test Paper-11

  • question_answer
    One mole of an ideal gas at an initial temperature of TK does 6R joules of work adiabatically. If the ratio of specific heats of this gas at constant pressure and at constant volume is 5/3, the final temperature of gas will be:

    A) \[(T+2.4)K\]                  

    B) \[(T-2.4)K\]

    C) \[(T+4)K\]                     

    D) \[(T-4)K\]   

    Correct Answer: D

    Solution :

     In an adiabatic process \[Q=0\] So, from the first law of thermodynamics \[W=-\Delta U=-n{{C}_{v}}\Delta \Tau =-n\left( \frac{R}{\gamma -1} \right)\] \[\Rightarrow \]\[W=\frac{nR}{\gamma -1}({{T}_{i}}-{{T}_{f}})\]                                    (i) Hence \[W=6R\,J,n=1\,mol,\] \[R=8.31\,J/mol-K,\gamma =\frac{5}{3},{{T}_{i}}=TK\] Substituting given values in Eq. (i), we get \[\therefore \]       \[6R=\frac{R}{5/3-1}(T-{{T}_{f}})\] \[\Rightarrow \]\[6R=\frac{3R}{2}(T-{{T}_{f}})\] \[\Rightarrow \]\[T-{{T}_{f}}=4\] \[\therefore \]\[{{T}_{f}}=(T-4)K\]


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