CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2011

  • question_answer
    The empirical formula of a non-electrolyte is\[C{{H}_{2}}O\]. A solution containing 3 g of the compound exerts the same osmotic pressure as that of 0.05 M glucose solution. The molecular formula of the compound is

    A)  \[C{{H}_{2}}O\]                               

    B)  \[{{C}_{2}}{{H}_{4}}{{O}_{2}}\]

    C)  \[{{C}_{4}}{{H}_{8}}{{O}_{4}}\]                 

    D)  \[{{C}_{3}}{{H}_{6}}{{O}_{3}}\]

    Correct Answer: B

    Solution :

    For isotonic solution (solution with same osmotic pressure) \[{{C}_{1}}={{C}_{2}}\]         \[\frac{{{W}_{x}}}{{{M}_{X}}}=\frac{{{W}_{{{C}_{6}}{{H}_{12}}{{O}_{6}}}}}{{{M}_{{{C}_{6}}{{H}_{12}}{{O}_{6}}}}}\]                 \[\frac{3}{{{M}_{x}}}=\frac{9}{180}\] \[0.05\,M\,{{C}_{6}}{{H}_{12}}{{O}_{6}}\] containing 9 g of glucose                 \[{{M}_{x}}=\frac{3\times 180}{9}=60\] Molecular weight of a non-electrolyte is 60 Molecular formula \[=n\times \] empirical formula Empirical formula \[=C{{H}_{2}}O\] Empirical formula mass \[=12+2+16=30\]                 \[n=\frac{molecular\text{ }mass}{empirical\text{ }formula\text{ }mass}\]                 \[=\frac{60}{30}=2\] Molecular formula \[=2\times C{{H}_{2}}O={{C}_{2}}{{H}_{4}}{{O}_{2}}\]


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