DUMET Medical DUMET Medical Solved Paper-2009

  • question_answer
    Common salt obtained from sea-water contains 95% NaCI by mass. The approximate number of molecules present in 10.0 g of the salt is

    A)  1021            

    B)  1022

    C)  1023            

    D)  1024

    Correct Answer: C

    Solution :

    In 10 g of sea water, amount of NaCI = 95% of 10 g \[=\frac{95\times 10}{100}=9.5\,g\] Molecular weight of NaCI = 23 + 35.5 = 58.5 \[\because \] 58.5 g of NaCI contains \[=6.023\times {{10}^{23}}\] molecules \[\therefore \] 9.5 g of NaCI will contain \[=\frac{6.023\times {{10}^{23}}\times 9.5}{58.5}\] \[\approx 1.0\times {{10}^{23}}\]


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