Question

The enamel present on teeth becomes much harder due to the conversion of hydroxyapatite into fluorapatite. What are \( X \) and \( Y \)?

• A. \( X = \text{Ca(OH)}_2, Y = \text{CaF}_2 \)
• B. \( X = \text{Ca(OH)}_2, Y = \text{CaCl}_2 \)
• C. \( X = \text{Ca(OH)}_2, Y = \text{NaCl} \)
• D. \( X = \text{CaO}, Y = \text{CaCl}_2 \)

Hint:

Fluoride strengthens enamel by converting hydroxyapatite into fluorapatite.

Answer 1

The Correct Option is A

Step 1: Understanding Tooth Enamel Hardening
- Hydroxyapatite: \( \text{Ca}_5(\text{PO}_4)_3\text{OH} \)
- Fluoride treatment replaces OH⁻ with F⁻, forming fluorapatite, which is stronger.
\[ 3\text{Ca}_5(\text{PO}_4)_3\text{OH} + F^- \rightarrow 3\text{Ca}_5(\text{PO}_4)_3\text{F} \]
- \( X = \text{Ca(OH)}_2 \) contributes OH⁻.
- \( Y = \text{CaF}_2 \) provides F⁻.