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JEE Main & Advanced Chemistry Some Basic Concepts of Chemistry / रसायन की कुछ मूलभूत अवधारणाएँ Question Bank Topic Test - Some Basic Concepts of Chemistry

  • question_answer
    Apatite is a mineral that is found in tooth enamel. When fluoride toothpastes are used, this mineral is converted to fluoroapatite, which is more resistant to tooth decay. The formula of apatite is \[C{{a}_{5}}{{(P{{O}_{4}})}_{x}}F\]. What is the value of \[x\] if the compound contains 18.45% by weight of phosphorus? (Atomic weight of \[P=31,\,\,Ca=40,\]\[F=19\] and \[O=16\])

    A) 2

    B) 4           

    C)       5

    D) 3

    Correct Answer: D

    Solution :

    [d] % of \[P=\frac{x\times 31}{5\times 40+31x+64x+19}\times 100=18.45\] \[\Rightarrow \]   \[x=3\]


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