111. Solving a chemistry problem

25 ml of an isotonic solution of NaCl, the density of which is 1.005 g/cm3, was poured into a column with an H-form cation exchanger. The column was then washed with water. 19.3 ml of 0.2 N NaOH solution was used for titration of the eluate obtained in this case with a correction factor of 0.9855. Determine the mass fraction of sodium chloride in an isotonic solution. Write an ion exchange equation.