JEE Main & Advanced JEE Main Solved Paper-2017

  • question_answer
    The temperature of an open room of volume \[30{{m}^{3}}\]increases from \[17{{\,}^{o}}C\]to\[27{{\,}^{o}}C\] due to sunshine. The atmospheric pressure in the room remains \[1\times {{10}^{5}}\,Pa.\] If \[{{n}_{i}}\]and \[{{n}_{f}}\] are the number of molecules in the room before and after heating, then \[{{n}_{f}}-{{n}_{i}}\]will be:-    JEE Main Solved Paper-2017

    A)  \[2.5\times {{10}^{25}}\]                            

    B) \[-2.5\times {{10}^{25}}\]

    C)  \[-1.61\times {{10}^{23}}\]                        

    D)  \[1.38\times {{10}^{23}}\]

    Correct Answer: B

    Solution :

     Using ideal gas equation PV = NRT (N is number of moles) \[{{P}_{0}}{{V}_{0}}={{N}_{i}}R\times 290\]                                         ?.. \[[{{T}_{i}}=237+17=290K]\] After heating \[{{P}_{0}}{{V}_{0}}={{N}_{f}}R\times 300\]                                         ?.. from equation [a] and [b] \[{{N}_{f}}-{{N}_{i}}=\frac{{{P}_{0}}{{V}_{0}}}{R}\left[ \frac{10}{290\times 300} \right]\] Hence \[{{n}_{f}}-{{n}_{i}}\]is \[=-\frac{{{P}_{0}}{{V}_{0}}}{R}\times \left[ \frac{10}{290\times 300} \right]\times 6.023\times {{10}^{23}}\] Putting \[{{P}_{0}}={{10}^{5}}{{P}_{A}}\]and \[{{V}_{0}}=30{{m}^{3}}\] Number of molecules \[{{n}_{f}}-{{n}_{i}}=-2.5\times {{10}^{25}}\]


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