NEET Sample Paper NEET Sample Test Paper-18

  • question_answer
    If one mole of a monatomic gas \[\gamma =\frac{5}{3}\]is mixed with one mole of a diatomic gas \[\gamma =\frac{7}{5},\]the value of \[\gamma \]for the mixture is

    A)  1.40                           

    B)  1.50

    C)  1.53                           

    D)  3.07

    Correct Answer: B

    Solution :

    Let,\[{{U}_{1}}\]be the internal energy of the monoatomic gas and the internal energy of the diatomic gas. Now, the internal energy of the mixture \[={{U}_{mix}}={{U}_{1}}+{{U}_{2}}.\] or,\[({{n}_{1}}+{{n}_{2}}){{C}_{{{v}_{mix}}}}={{n}_{1}}{{C}_{{{v}_{1}}}}T+{{n}_{2}}{{C}_{{{v}_{2}}}}T\]             \[\Rightarrow \]\[{{C}_{{{v}_{mix}}}}=\frac{{{n}_{1}}{{C}_{{{v}_{1}}}}+{{n}_{2}}{{C}_{{{v}_{2}}}}}{{{n}_{1}}+{{n}_{2}}}=\frac{1\times \frac{3R}{2}+1\times \frac{5R}{2}}{1+1}=2R\]             \[\therefore \]      \[\frac{R}{{{\gamma }_{mix}}-1}=2R\]             \[\Rightarrow \]\[{{\gamma }_{mix}}=\frac{3}{2}=1.5\] Hence, the correction option is [b].


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