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9th Class Science Atoms and Molecules Question Bank Atoms and Molecules

  • question_answer
    An ionic compound of element/Wand chlorine has the formula, \[\text{MC}{{\text{l}}_{\text{3}}}\]. The molecular mass of \[\text{MC}{{\text{l}}_{3}}\] is 118.5. What will be the molecular mass of the oxide of element M?

    A) 28                               

    B) 44                   

    C) 72                   

    D)        99                   

    Correct Answer: C

    Solution :

    The valency of M in is +3 hence, the formula of the oxide of element M is \[{{\text{M}}_{\text{2}}}{{\text{O}}_{\text{3}}}\]. Mass of element M in\[\text{MC}{{\text{l}}_{\text{3}}}\text{=118}\text{.5-3(35}\text{.5)=12}\] Molecular mass of \[{{\text{M}}_{\text{2}}}{{\text{O}}_{\text{3}}}=(2\times 12)+(3\times 16)=72\]


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