Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2005

  • question_answer
    Air is filled at \[60{}^\circ C\] in a vessel of open mouth. The vessel is heated to a temperature T so that \[\frac{1}{4}\]th part of air escapes. The value of T is

    A) \[80{}^\circ C\]

    B) \[444{}^\circ C\]

    C) \[333{}^\circ C\]

    D) \[171{}^\circ C\]

    Correct Answer: D

    Solution :

    Since, vessel is open, therefore p remains constant so by Charles' law \[\frac{{{V}_{1}}}{{{V}_{2}}}=\frac{{{T}_{1}}}{{{T}_{2}}}\]                 \[\because \]     \[V=\frac{m}{\rho }\]                 or            \[V\propto \frac{1}{\rho }\]                 \[\Rightarrow \]               \[\frac{{{V}_{1}}}{{{V}_{2}}}=\frac{{{\rho }_{2}}}{{{\rho }_{1}}}\]                 \[\therefore \]  \[\frac{{{\rho }_{2}}}{{{\rho }_{1}}}=\frac{{{T}_{1}}}{{{T}_{2}}}\]                 or            \[{{\rho }_{1}}{{T}_{1}}={{\rho }_{2}}{{T}_{2}}\]                 \[\because \]     \[{{\rho }_{1}}=\frac{m}{V},\] \[{{\rho }_{2}}=\frac{m-m/4}{V}=\frac{3m}{4V},\]                                 \[{{T}_{1}}=60+273=333K\]                                 \[{{T}_{2}}=\frac{{{\rho }_{1}}}{{{\rho }_{2}}}.{{T}_{1}}=\frac{4}{3}\times 333=444K\]                 or            \[={{171}^{o}}C\]


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