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JEE Main · 2018 · 08 Apr 2018 · Offline · s-Block Elements

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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 to :
  1. (A)
  2. (B)
  3. (C)
  4. (D)✓ Correct

Answer: (D)

Solution

Tooth enamel is mainly hydroxyapatite, , and a trace of fluoride hardens it by swapping the hydroxide for fluoride. The calcium phosphate framework is left untouched while the part becomes , converting the mineral to the tougher, more acid-resistant fluorapatite .

JEE Main · 2018 · 08 Apr 2018 · Offline · Single correct option

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