Question

The concentration of fluoride ions in drinking water upto $1\, ppm$ make the enamel on teeth much harder by converting $\underline{X}$ into fluorapatite. What is $\underline{X}$ ?

• A. $\left[3 Ca _{3}\left( PO _{4}\right)_{2} \cdot CaF _{2}\right]$
• B. $\left[3 Ca _{2}\left( PO _{4}\right)_{2} \cdot Ca ( OH )_{2}\right]$
• C. $\left[3 Ca ( OH )_{2} \cdot Ca _{3}\left( PO _{4}\right)_{2}\right]$
• D. $\left[ Ca _{3}\left( PO _{4}\right)_{2} \cdot 3 CaF _{2}\right]$

Answer 1

Answer: (B)

Fluoride is a chemical element that is found most frequently in ground water. Fluoride has a great affinity for the developing enamel because teeth apatite crystals have the capacity to bind and integrate fluoride ion into the crystal lattice. The concentration of fluoride ions in drinking water upto $1 \,ppm$ make the enamel on teeth much harder by converting $\left[3 Ca _{3}\left( PO _{4}\right)_{2} \cdot Ca ( OH )_{2}\right]$ into fluorapatite $\left[3 Ca _{3}\left( PO _{4}\right)_{2} \cdot CaF _{2}\right]$

$\underset{(X)}{\left[3 Ca _{3}\left( PO _{4}\right)_{2} \cdot Ca ( OH )_{2}\right]} \ce{->[{ F ^{-}}][{1\text{ppm}}]} \underset{\text{(Fluorapatite)}}{\left[3 Ca _{3}\left( PO _{4}\right)_{2} \cdot CaF _{2}\right]}$