111. Solving a chemistry problem

516. A portion of a sample containing copper (II), weighing 3.1012 g, was dissolved in a volumetric flask with a volume of 100.0 ml. An aliquot of the resulting solution with a volume of 10.00 ml was treated with an excess of potassium iodide, and the released iodine was titrated with 9.85 ml of a 0.05000 mol/l solution of sodium thiosulfate. Calculate the mass fraction of copper(II) in the sample as a percentage.