121. Solving a chemistry problem

10. Calculate the mass fraction of lead in the sample, if after dissolving its sample weighing 0.5433 g, 25.00 ml of K2CrO4 solution was added to the resulting solution, the resulting precipitate was filtered, an excess of KI was added to the filtrate, and the released iodine was titrated with 15.20 ml of 0.1000 M Na2S2O3 solution (1.00 ml potassium chromate is equivalent to 1.20 ml Na2S2O3 solution).