Assertion: Soluble fluoride is often added to drinking water to bring its concentration up to 1 ppm. Reason: F- ion concentration above 2 ppm causes brown mottling of teeth.

Question

Assertion: Soluble fluoride is often added to drinking water to bring its concentration up to 1 ppm. Reason: F- ion concentration above 2 ppm causes brown mottling of teeth. (A) If both assertion and reason are true and reason is the correct explanation of assertion (B) If both assertion and reason are true but reason is not the correct explanation of assertion (C) If assertion is true but reason is false (D) If both assertion and reason are false

Tardigrade Admin · Accepted Answer

F- ions make the enamel on teeth much harder by converting hydroxyapatite, [3(Ca3(PO4 )2) ⋅ Ca(OH)2], the enamel on the surface of the teeth, into much harder fluorapatite [3(Ca3(PO4)2)⋅ CaF2].

Q. Assertion : Soluble fluoride is often added to drinking water to bring its concentration up to $1 pp m$ .
Reason : $F^{-}$ ion concentration above $2 pp m$ causes brown mottling of teeth.

If both assertion and reason are true and reason is the correct explanation of assertion

If both assertion and reason are true but reason is not the correct explanation of assertion

If assertion is true but reason is false

If both assertion and reason are false

$F^{-}$ ions make the enamel on teeth much harder by converting hydroxyapatite, $[3 (C a_{3} (P O_{4})_{2}) \cdot C a (O H)_{2}]$ , the enamel on the surface of the teeth, into much harder fluorapatite $[3 (C a_{3} (P O_{4})_{2}) \cdot C a F_{2}]$ .

Q. Assertion : Soluble fluoride is often added to drinking water to bring its concentration up to 1ppm. Reason : F− ion concentration above 2ppm causes brown mottling of teeth.