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We learned that fluoride is an essential element to be taken to
reduce
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teeth
cavities. Too much fluoride can
produce yellow spots on the teeth
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and too little
will have no effect. After years of
study it was determined
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that a quantity
of 1 part per million (ppm) fluoride in the water supply is
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enough to
significantly reduce cavities and not stain teeth yellow.
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Measure the mass of the mineral fluorite
(chemically, CaF2). Use this
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sample to
determine how much water must be added to yield a 1 ppm
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fluoride
solution. Sounds difficult? Lets apply what we’ve learned this
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unit to solve
this problem.
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1 part
per million = 1 atom of fluorine per 999,999 water
molecules
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What
information do we know:
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1 mol
CaF2 = 78.08 g CaF2 =
6.02 x 1023 molecules of CaF2
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1
molecules of CaF2 = 2 atoms of F
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1 mol
H2O = 18 g H2O Density of water is 1 g/mL
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1000
mL =
1 L and 3.78 L
= 1 gallon
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mass
of sample of CaF2 = 92.135 g
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