13. Solving a chemistry problem

10. A sample of contaminated soda weighing 0.2110 g is dissolved in 25 ml of a solution of hydrochloric acid with a concentration of c(HCl)=0.2022 mol/l. The excess HCl is titrated with 5.50 ml of NaOH solution, 1 ml of which is equivalent to 1.033 ml of HCl. Determine the mass fraction (%) of Na2CO3 in contaminated soda.