Question

A 591 mL bottle of fortified water contains 32 mg of potassium ions.

a. What is the molarity of the potassium ions?

B. How many potassium ions are in this bottle?

Answer 1

K+ mass = 32 mg = 0.032 g

K+ molar mass = 39 g / mol

moles of K+ = 0.032 / 39

                   = 8.20x 10^-4

molarity = moles / volume (Litres)

               = 8.20x 10^-4 / 0.591

              = 1.39 x 10^-3 M

molarity = 1.39 x 10^-3 M

B)

number of potassium ions = 8.20x 10^-4 x 6.023 x 10^23

                                         = 4.94 x 10^20