39. Solving a chemistry problem

11. To determine lead in the ore, a 5.0000 g sample of the ore was taken; when dissolved in acid, the Pb2+ ion precipitated in the form of lead chromate. The precipitate is filtered off and dissolved in a mixture of potassium iodide and hydrochloric acid. The iodine released as a result of the reaction was titrated with 0.05000 N. thiosulfate solution, which consumed 42.00 ml. How much lead (in%) does the ore contain?