Question

In order to make tooth enamel stronger by converting $[3{\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2.\mathrm{Ca}{\left(\mathrm{OH}\right)}_2]$ to, the suggested fluoride ion concentration in drinking water is up to ,$1\mathrm{ppm}$.

• A. $[3\mathrm{Ca}{\left(\mathrm{F}\right)}_2.\mathrm{Ca}{\left(\mathrm{OH}\right)}_2]$
• B. $[3{\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2.{\mathrm{CaF}}_2]$
• C. $[3\mathrm{Ca}{\left(\mathrm{OH}\right)}_2.\mathrm{Ca}{\left(\mathrm{F}\right)}_2]$
• D. $\left[{\mathrm{CaF}}_2\right]$

Answer 1

The correct option is B

$[3{\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2.{\mathrm{CaF}}_2]$

The explanation for the correct option:

B: $[3{\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2.{\mathrm{CaF}}_2]$

Fluoride Ion:

• By strengthening the enamel's resistance to acid attack, fluoride helps prevent tooth decay.
• They also quicken the process of good minerals accumulating in the enamel, further delaying the onset of tooth deterioration.
• Studies also suggest that fluoride may occasionally be able to halt tooth decay that has already begun.

Conversion:

• ${\mathrm{F}}^{-}$ ions harden the enamel of the teeth by converting:
• $[3{\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2.\mathrm{Ca}{\left(\mathrm{OH}\right)}_2]\mathrm{to}[3{\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2.{\mathrm{CaF}}_2]$

Final answer: Hence, the correct answer is option B, $[3{\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2.{\mathrm{CaF}}_2]$.