Apatite is a mineral that is found in tooth enamel. When fluoride toothpastes are used, this mineral is converted to fluoroapatite, which is much harder and therefore more resistant to decay. What is the percent by weight of fluorine in fluoroapatite, Ca₅(PO₄)₃F?

Question

Quizplus · Accepted Answer

The formula for fluoroapatite is Ca5(PO4)3F. To find the percent by weight of fluorine in fluoroapatite, calculate the molar mass of the compound and the molar mass of fluorine within it. The molar mass of fluoroapatite is the sum of the molar masses of its constituents: 5Ca + 3P + 12O + F. Using approximate atomic masses (Ca = 40, P = 31, O = 16, F = 19), the molar mass of fluoroapatite is approximately 5(40) + 3(31) + 12(16) + 19 = 502. The percent by weight of fluorine is then (19/502) * 100%, which is approximately 3.78%, placing it in the range of between 3% and 5%.

Apatite Is a Mineral That Is Found in Tooth Enamel