Final answer:
To convert 2.4 ppm F- to molarity of fluoride ion, divide the mass of F- by the molar mass and the volume of the solution. The molarity of fluoride ion would be approximately 0.1264 M.
Step-by-step explanation:
The conversion from ppm (parts per million) to molarity involves the use of the molar mass and the volume of the solution. In this case, the formula unit of fluoride ion is F-. We can convert 2.4 ppm F- to molarity by first determining the mass of F- in the given volume, and then dividing that mass by the molar mass and the volume to find the molarity.
First, let's assume we have 1 liter (1000 mL) of solution. The given concentration of 2.4 ppm F- means that there are 2.4 milligrams of F- in every liter of solution.
To convert milligrams to moles, we need to divide the mass by the molar mass of F-. The molar mass of F- is approximately 18.998 g/mol.
Next, we divide the moles by the volume of the solution to get the molarity. Since we assumed 1 liter of solution, the molarity would be equal to the moles of F-. However, if the volume is given in mL, we would need to convert the volume to liters by dividing it by 1000.
So, in this case, the molarity of fluoride ion would be (2.4 mg / 18.998 g/mol) / 1 L = 0.1264 mol/L, or approximately 0.1264 M.