Question

express the concentration of a 0.0700 M aqueous solution of fluoride, F-, in mass percentage and in parts million. Assume the density of the solution is 1.00 g/mL.

Answer 1

F- molar mass = 19 g/mol

molarity = 0.0700 M

molarity = 0.0700 mole / L

             = 0.0700 g/L x 19

           = 1.33 g /L

            = 1330 mg /L

            = 1330 ppm                          ( since : mg/L = ppm)

solution mass = 1.00 g / mL ) x 1000 mL

                      = 1000 g

in 1 Litre mass of F - = 1.33 g

mass % =( mass of F- / solution mass ) x 100

              = (1.33 / 1000) x 100

             = 0.133 %