NEET Sample Paper NEET Sample Test Paper-50

  • question_answer With what minimum pressure in Kpa of given volume of an ideal gas \[\left( Cp\,\,=\,\,\frac{7}{2}R \right)\] originally   at 400 K and 100 kPa pressure, be adiabatically compressed in order to raise its temperature to 600 K-

    A) 362.5 kpa                     

    B) 275 kpa

    C) 437.5 kpa                     

    D) 550 kpa

    Correct Answer: B

    Solution :

    For an adiabatic irrereversible compression, \[\Delta E\,\,=\,\,W\] \[\therefore \,\,\,n{{C}_{v}}\left( {{T}_{2}}-{{T}_{1}} \right)=-\,{{P}_{ext}}\left( V{{ & }_{2}}-{{V}_{1}} \right)\] \[\therefore \,\,\,n{{C}_{v}}\left( {{T}_{2}}-{{T}_{1}} \right)=-\,{{P}_{2}}\,\left( \frac{nR{{T}_{2}}}{{{P}_{2}}}-\frac{nR{{T}_{1}}}{{{P}_{1}}} \right)\] \[=\,\,n\times \frac{5}{2}R\,({{T}_{2}}-{{T}_{1}})\,\,=\,\,-{{P}_{2}}\times nR\,\left[ \frac{{{T}_{2}}}{{{P}_{2}}}-\frac{{{T}_{1}}}{{{P}_{1}}} \right]\] \[=\,\frac{5}{2}\times \,\,(600-400)\,\,=\,\,-{{P}_{2}}X\,\left[ \frac{600}{{{P}_{2}}}-\frac{400}{100} \right]\] \[{{P}_{2}}\,\,=\,\,275\,Kpa.\]


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