1011. Solving a chemistry problem

1. A sample of technical sodium chromate tetrahydrate weighing 0.500 g was dissolved in a 100 ml volumetric flask. To 10.0 ml of the resulting solution, 20.0 ml of a solution of iron(II) sulfate with a molar concentration of 0.055 mol/l was added; 11.1 ml of a solution of potassium permanganate with a concentration of 0.05 N was spent on titrating the excess. Calculate the mass fraction of sodium chromate tetrahydrate in the sample.