Chemistry (2018) | JEE 2018 | Discussion Page

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

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

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Answer:

Explanation: