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BCECE Engineering BCECE Engineering Solved Paper-2002

  • question_answer
    A \[CaC{{O}_{3}}\]sample contains \[3.01\times {{10}^{23}}\] ions of \[\overset{2+}{\mathop{Ca}}\,\]and \[C{{O}_{3}}^{2-}.\]The mass of sample is:

    A) 40                          

    B)        50

    C) 60                          

    D)        70

    Correct Answer: B

    Solution :

    Key Idea:\[\text{Moles}\,\text{=}\,\,\frac{\text{Mass}}{\text{Molecular}\,\text{mass}}\] or   Mass = Moles \[\times \] molecular mass Molecular mass of \[CaC{{O}_{3}}\] \[40+12+16\times 3=40+12+48=100\] Moles of \[CaC{{O}_{3}}=\frac{3.01\times {{10}^{23}}}{6.02\times {{10}^{23}}}=0.5\] Mass of a \[CaC{{O}_{3}}=0.5\times 100=50\,g\]


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