JEE Main & Advanced
Sample Paper
JEE Main Sample Paper-46
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 :
% of \[P=\frac{x\times 31}{5\times 40+31x+64x+19}\times 100=18.45\]\[\Rightarrow \]\[x=3\]