CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2010

  • question_answer
    The empirical formula of a non-electrolyte is \[C{{H}_{2}}O\]. A solution containing 6 g of the compound exerts the same osmotic pressure as that of 0.05 M glucose solution at the same temperature. The molecular formula of the compound is

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

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

    C)   \[{{C}_{5}}{{H}_{10}}{{O}_{5}}\]               

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

    Correct Answer: D

    Solution :

    Solutions having same osmotic pressure, at a given temperature, have same concentration. Concentration of compound = concentration of glucose                 \[\frac{6}{M\times 1}=0.05\]                                 \[M=\frac{6}{0.05}=120\] Empirical formula mass \[(C{{H}_{2}}O)=12+2+16\]                                                                 = 30                 \[n=\frac{molecular\text{ }mass}{empirical\text{ }formula\text{ }mass}\]                 \[=\frac{120}{30}=4\] Hence, molecular formula                                                 \[=(C{{H}_{2}}{{O}_{4}})={{C}_{4}}{{H}_{8}}{{O}_{4}}\]


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