JEE Main & Advanced JEE Main Paper (Held on 09-4-2019 Morning)

  • question_answer Liquid 'M' and liquid 'N' form an ideal solution. The vapour pressures of pure liquids 'M' and 'N' are 450 and 700 mmHg, respectively, at the same temperature. Then correct statement is:
    (\[{{x}_{M}}\] = Mole fraction of 'M' in solution ;
    \[{{x}_{N}}\] = Mole fraction of 'N' in solution ;
    \[{{y}_{M}}\] = Mole fraction of 'M' in vapour phase ;
    \[{{y}_{N}}\] = Mole fraction of 'N' in vapour phase)
                [JEE Main 9-4-2019 Morning]

    A) \[({{x}_{M}}-{{y}_{M}})<({{x}_{N}}-{{y}_{N}})\]     

    B) \[\frac{{{x}_{M}}}{{{x}_{N}}}<\frac{{{y}_{M}}}{{{y}_{N}}}\]

    C) \[\frac{{{x}_{M}}}{{{x}_{N}}}>\frac{{{y}_{M}}}{{{y}_{N}}}\]       

    D) \[\frac{{{x}_{M}}}{{{x}_{N}}}=\frac{{{y}_{M}}}{{{y}_{N}}}\]

    Correct Answer: C

    Solution :

                \[\because P_{N}^{o}>P_{M}^{o}\]           \[\therefore y_{N}^{{}}>X_{N}^{{}}\]\[\And \,X_{M}^{{}}>y_{M}^{{}}\] Multiply we get \[y_{N}^{{}}X_{M}^{{}}>{{X}_{N}}{{y}_{M}}\] \[\therefore \]Ans. is [c]


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