Some Basic Concepts of Chemistry / रसायन की कुछ मूलभूत अवधारणाएँ
JEE Main & Advanced
Chemistry
Some Basic Concepts of Chemistry / रसायन की कुछ मूलभूत अवधारणाएँ
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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 \[P=\frac{x\times 31}{5\times 40+31x+64x+19}\times 100=18.45\] \[\Rightarrow \] \[x=3\]