11. A sample of ore containing manganese (IV) oxide, weighing 0.10 g, was treated with concentrated hydrochloric acid. The resulting chlorine was distilled off and absorbed with a solution of potassium iodide. The released iodine was titrated with 21.25 ml of 0.0520 N sodium thiosulfate solution. Calculate the mass fraction (%) of manganese oxide in the ore.

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