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Question:

The recommended concentration of fluoride ion in drinking water is up to 1 ppm. Fluoride ion is by converting [3Ca3(PO4)2.Ca(OH)2] to:

[CaF2]

[3Ca3(OH)2.CaF2]

[3Ca3(PO4)2.CaF2]

[3(CaF2).Ca(OH)2]

Solution:

The Fluoride ion converts [3Ca3(PO4)2.Ca(OH)2] to [3Ca3(PO4)2.CaF2]. The reaction can be given as follows: [3Ca3(PO4)2.Ca(OH)2] (drinking water up to 1 ppm) + 2F⁻ → [3Ca3(PO4)2.CaF2] (harder teeth enamel) Hence, the correct option is [3Ca3(PO4)2.CaF2]