Answer is: molarity of a potassium iodide solution is 3.2 M.
n(KI) =0.400 mol; amount of substance for potassium iodide.
V(solution) = 125 mL ÷ 1000 mL/L.
V(solution) = 0.125 L; volume of solution.
c(KI) = n(KI) ÷ V(solution).
c(KI) = 0.4 mol ÷ 0.125 L.
c(KI) = 3.2 mol/L; concentration of potassium iodide solution.
