JEE Main On 08 April 2018 Question 21
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 $ [3Ca _3{{(PO _4)}_2}\cdot Ca{{(OH)}_2}] $ to: [JEE Main Online 08-04-2018]
Options:
A) $ [3Ca _3{{(PO _4)}_2}\cdot CaF _2] $
B) $ [3{Ca{{(OH)}_2}}\cdot CaF _2] $
C) $ [CaF _2] $
D) $ [3(CaF _2)\cdot Ca{{(OH)}_2}] $
Show Answer
Answer:
Correct Answer: A
Solution:
- The $ {F^{–}} $ ion makes the enamel on teeth much harder by converting hydroxyapatite $ [\text{ 3C}{a_3}{{\text{(P}{O_4}\text{)}}_2}\text{.Ca(OH}{{)}_2}] $ into much harder Fluor apatite $ [\text{ 3C}{a_3}{{\text{(P}{O_4}\text{)}}_2}\text{.Ca}{F_2}] $ .
