KVPY Sample Paper KVPY Stream-SX Model Paper-6

  • question_answer
    Two beaker A and B present in a closed vessel. Beaker A contains 152.4 g aqueous solution of urea, containing 12 g of urea beaker B contains 196.2 g glucose solution, containing 18 g of glucose. Both solutions allowed to attain the equilibrium. The mass % of glucose in its solution at equilibrium is

    A) \[6.71\]             

    B) \[14.49\]

    C) \[16.94\]                       

    D) \[20\]

    Correct Answer: B

    Solution :

    Mole fraction of urea in its solution \[=\frac{\frac{12}{60}}{\frac{12}{60}+\frac{140.4}{18}}\Rightarrow 0.025\]
    Mole fraction of glucose \[=\frac{\frac{18}{180}}{\frac{18}{180}+\frac{178.2}{18}}\Rightarrow 0.01\]
    \[\because \]Mole fraction of glucose is less so vapour pressure above the glucose solution will be higher than the pressure above urea solution, so some \[{{\operatorname{H}}_{2}}O\]molecules will transfer from glucose to urea side in order to make the solutions of equal mole fraction to attain equilibrium, let \[x\]moles \[{{\operatorname{H}}_{2}}O\]transferred
    \[\therefore \]\[\frac{0.2}{0.2+7.8+x}=\frac{0.1}{0.1+9.9-x}\Rightarrow x=4\]
    Now mass of glucose solution \[\Rightarrow 196.2-4\times 18\Rightarrow 124.2\]
    wt. % of glucose\[=\frac{18}{124.2}\times 100\Rightarrow 14.49\]


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