Problem: Tooth enamel consists of hydroxyapatite, Ca 5(PO4)3OH (Ksp = 6.8 × 10−37). Fluoride ion added to drinking water reacts with Ca5(PO4)3OH to form the more tooth decay–resistant fluorapatite, Ca5(PO4)3F (Ksp = 1.0 × 10−60). Fluoridated water has dramatically decreased cavities among children. Calculate the solubility of Ca5(PO4)3OH and of Ca 5(PO4)3F in water.

FREE Expert Solution

For Ca5(PO4)3OH: Since the Ca5(PO4)3OH is an ionic compound, it forms ions when dissociating in water. The dissociation of Ca5(PO4)3OH in water is as follows:

Ca5(PO4)3OH(s)  5 Ca2+(aq) + 3 PO43+(aq) +  OH(aq)



We can construct an ICE table for the dissociation of Ca5(PO4)3OH

Remember that solids are ignored in the ICE table and Ksp expression.

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Problem Details

Tooth enamel consists of hydroxyapatite, Ca 5(PO4)3OH (Ksp = 6.8 × 10−37). Fluoride ion added to drinking water reacts with Ca5(PO4)3OH to form the more tooth decay–resistant fluorapatite, Ca5(PO4)3F (Ksp = 1.0 × 10−60). Fluoridated water has dramatically decreased cavities among children. Calculate the solubility of Ca5(PO4)3OH and of Ca 5(PO4)3F in water.

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Our data indicates that this problem or a close variation was asked in Chemistry: The Molecular Nature of Matter and Change - Silberberg 8th Edition. You can also practice Chemistry: The Molecular Nature of Matter and Change - Silberberg 8th Edition practice problems.