The conversion of hydroxyapatite occurs due to presence of $\mathrm{F}^{-}$ions in water. The correct formula of hydroxyapatite is:

(B) $\left[3 \mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2} \cdot \mathrm{Ca}(\mathrm{OH})_{2}\right]$

(A) $\left[\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2} \cdot \mathrm{CaF}_{2}\right]$

(C) $\left[3 \mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2} \cdot \mathrm{CaF}_{2}\right]$

(D) $\left[3 \mathrm{Ca}(\mathrm{OH})_{2} \cdot \mathrm{CaF}_{2}\right]$

JEE Main · 2021 · 26 Aug 2021 · Shift 1 · s-Block Elements

The conversion of hydroxyapatite occurs due to presence of

F^{-}

ions in water. The correct formula of hydroxyapatite is:

Answer: (B)

Hydroxyapatite is the calcium phosphate of tooth enamel,

C a_{10} (P O_{4})_{6} (OH)_{2}

, which written in the double-salt style is

3 C a_{3} (P O_{4})_{2} \cdot Ca (OH)_{2}

. Fluoride ion present in drinking water replaces the hydroxide of this lattice and converts it to fluorapatite,

3 C a_{3} (P O_{4})_{2} \cdot Ca F_{2}

, which is far less soluble in the acids produced by mouth bacteria. The correct formula of hydroxyapatite is

3 C a_{3} (P O_{4})_{2} \cdot Ca (OH)_{2}

JEE Main · 2021 · 26 Aug 2021 · Shift 1 · Single correct option