38. Solving a chemistry problem

765. When determining sodium in the analyzed sample of sodium salt, a strongly acid cation exchanger KU-2 in the H-form was used. A weighed sample of mass m was dissolved in water in a volumetric flask with a capacity of Vk(x), the volume of the solution was brought up to the mark with water, and the analyzed solution was obtained. An aliquot of the analyzed solution with a volume of Va(x) was passed through a chromatographic column with a cation exchanger in
H-form and after washing the column with water, the collected eluate was titrated with a sodium hydroxide solution with a molar concentration of C(KOH), while spending V(KOH) ml of the titrant solution.
Write the equation for the reaction of ion exchange between the cation exchanger (R–H) and the analyzed solution passed through the cation exchanger in molecular and ionic form. From the data below, calculate the mass fraction (%) of sodium in the analyzed sample.
Why is it not recommended to use the above method in the analysis of salts containing anions of weak acids, for example, in the analysis of sodium acetate?
Variant Salt sample m, g Vk(x), ml Va(x), ml C(NaOH), mol/l V(NaOH), ml
e Na2SO4 • 10H2O 2.2600 50 10.00 0.1035 13.57