Question

The conversion of hydroxyapatite occurs due to presence of \(F^-\) ions in water. The correct formula of hydroxyapatite is :

• A. \([3Ca_3(PO_4)_2 \cdot CaF_2]\)
• B. \([Ca_3(PO_4)_2 \cdot CaF_2]\)
• C. \([3Ca_3(PO_4)_2 \cdot Ca(OH)_2]\)
• D. \([3Ca(OH)_2 \cdot CaF_2]\)

Hint:

Think of "hydroxy" as signifying the presence of hydroxide groups (\(OH^-\)). The conversion to "fluorapatite" is why fluoride is added to toothpaste—it makes teeth stronger!

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Tooth enamel is primarily composed of hydroxyapatite, a calcium phosphate mineral. Fluoride ions can replace the hydroxyl groups in this structure to form fluorapatite, which is harder and more resistant to acid.
Step 2: Detailed Explanation:
1. Hydroxyapatite is a complex mineral with the formula \([3Ca_3(PO_4)_2 \cdot Ca(OH)_2]\) or \(Ca_{10}(PO_4)_6(OH)_2\).
2. When fluoride ions are present in drinking water, they replace the \(OH^-\) ions in hydroxyapatite to form fluorapatite, \([3Ca_3(PO_4)_2 \cdot CaF_2]\).
3. The question specifically asks for the formula of hydroxyapatite, which is the hydroxyl-containing form.
Step 3: Final Answer:
The formula of hydroxyapatite is \([3Ca_3(PO_4)_2 \cdot Ca(OH)_2]\).