NEET Sample Paper NEET Sample Test Paper-49

  • question_answer
    The molarity of a solution of ethanol in water in which the mole fraction of \[{{C}_{2}}{{H}_{5}}OH\] is 0.040 is- (assume density of solution to be 1 g/ml)

    A) 2.09 M             

    B) 2.31 M

    C) 20.9 M             

    D) 23.1M

    Correct Answer: A

    Solution :

    \[{{X}_{{{C}_{2}}{{H}_{5}}OH}}\,\,=\,\,0.040\] \[{{X}_{{{H}_{2}}O}}\,\,=\,\,0.96\] \[\frac{{{X}_{{{C}_{2}}{{H}_{5}}OH}}}{{{X}_{{{H}_{2}}O}}\,}\,\,=\,\,\frac{0.04}{0.96}\,\,=\,\,\frac{1}{24}\,\,\,\therefore \,\frac{{{n}_{{{C}_{2}}{{H}_{5}}OH}}}{{{n}_{{{H}_{2}}O}}}\,\,=\,\,\frac{1\,\,mol}{24\,\,mol}\] \[\therefore \] Total wt. of solution \[=\text{ }46+24\times 18=478g\] \[d\,\,=\,\,1~\,\,\,\,\,\,\,\,\,\therefore \,\,\,\text{ }V\,\,=\,\,478\text{ }ml\] \[Molarity\,\,=\,\,\frac{{{n}_{{{C}_{2}}{{H}_{5}}OH}}}{V}\,\,=\,\,\frac{1\times 1000}{478}\,\,=\,\,2.09\,\,M\]


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