Discussion Forum



1)

The recommended concentration of fluoride ion in drinking water is up to 1 ppm as fluroide ion is required to make teeth enamel harder by converting [3Ca3(PO4)2.Ca (OH)2]  to


A) [$CaF_{2}$]

B) [$3(CaF_{2}).Ca(OH)_{2}$]

C) [$3Ca_{3}(PO_{4})_{2}.CaF_{2}$]

D) [3{$Ca_{3}(PO_{4})_{2}$}.$CaF_{2}$]

Answer:

Option C

Explanation:

Fluoride ions help in making teeth enamel harder by converting [3Ca3(PO4)2.Ca(OH)2] i.e. Hydroxyapatite to [3Ca3(PO4)2.CaF2] i.e., Fluorapatite (Harder teeth enamel) via the following the reaction

  $\left[3Ca_{3}\left(PO_{4}\right)_2.Ca\left(OH\right)_2\right]+2F^{-} \rightarrow$  $[3Ca_{3}(PO_{4})_{2}.CaF_{2}]$   +  $2OH^{-}$