Question
The recommended concentration of fluoride ion in drinking water is up to $$1ppm$$ as fluoride ion is required to make teeth enamel harder by converting $$\left[ {3C{a_3}{{\left( {P{O_4}} \right)}_2}.Ca{{\left( {OH} \right)}_2}} \right]$$
A.
$$\left[ {Ca{F_2}} \right]$$
B.
$$\left[ {3\left( {Ca{F_2}} \right).Ca{{\left( {OH} \right)}_2}} \right]$$
C.
$$\left[ {3C{a_3}{{\left( {P{O_4}} \right)}_2}.Ca{F_2}} \right]$$
D.
$$\left[ {3\left\{ {\left( {Ca{{\left( {OH} \right)}_2}} \right.} \right\}.Ca{F_2}} \right]$$
Answer :
$$\left[ {3C{a_3}{{\left( {P{O_4}} \right)}_2}.Ca{F_2}} \right]$$
Solution :
$$\mathop {\left[ {3C{a_3}{{\left( {P{O_4}} \right)}_2}.Ca{{\left( {OH} \right)}_2}} \right]}\limits_{{\text{Hydroxyapatite}}} + \mathop {2{F^ - }}\limits_{\left( {{\text{drinking}}\,{\text{water}}\,{\text{upto}}\,{\text{1ppm}}} \right)} \to \mathop {\left[ {3C{a_3}{{\left( {P{O_4}} \right)}_2}.Ca{F_2}} \right] + 2O{H^ - }}\limits_{{\text{Fluorapatite}}\left( {{\text{Harder}}\,{\text{teeth}}\,{\text{enamel}}} \right)} $$