Fluoridation is the process of adding fluorine compounds to drinking water to
help fight tooth decay. A concentration of 1 ppm of fluorine is sufficient for
the purpose. (1 ppm means \(1 \mathrm{~g}\) of fluorine per 1 million g of
water.) The compound normally chosen for fluoridation is sodium fluoride,
which is also added to some toothpastes. Calculate the quantity of sodium
fluoride in kilograms needed per year for a city of 50,000 people if the daily
consumption of water per person is 150 gallons. What percent of the sodium
fluoride is "wasted" if each person uses only \(6.0 \mathrm{~L}\) of water a day
for drinking and cooking? (Sodium fluoride is 45.0 percent fluorine by mass. 1
gallon \(=3.79 \mathrm{~L} ; 1\) year \(=365\) days; density of water \(=1.0
\mathrm{~g} / \mathrm{mL} .)\)