Question

The recommended concentration of fluoride ion in drinking water is up to 1 ppm as fluoride ion is required to make teeth enamel harder by converting $\left[\right.3Ca_{3}\left(P O_{4}\right)_{2}.Ca\left(O H\right)_{2}\left]\right.$ to

• A. $\left[3\left( Ca ( OH )_{2}\right) \cdot CaF _{2}\right]$
• B. $\left[C a F_{2}\right]$
• C. $\left[3 \left(C a F_{2}\right) . C a \left(O H\right)_{2}\right]$
• D. $\left[\right.3Ca_{3}P O_{4} \left._{2} . C a F_{2}\right]$

Answer 1

Answer: (D)

$\left[3 Ca _{3}\left( PO _{4}\right)_{2} \cdot Ca ( OH )_{2}\right]+2 F ^{-} \rightarrow\left[3 Ca _{3}\left( PO _{4}\right)_{2} \cdot CaF _{2}\right]+2 OH ^{-}$