Fluoride ion is added to drinking water at low concentra- tions to prevent tooth decay. What mass of sodium fluoride (NaF) should be added to 750 L of water to make a solution that is 1.5 ppm in fluoride ion? (LO 13.5) (a) 1.1 g (b) 2.5 g (c) 0.51 g (d) 3.1 g