138. Задачка по химии №013 834

94. To determine the impurity of ethyl alcohol in ether, it was distilled off from a sample of ether 3.5000 g. The resulting distillate was treated with 10.00 cm3 0.2000 n K2CrO7 in a sulfuric acid medium with heating. After cooling and dilution with water, 5 cm3 of a 10% KI solution was added to this solution, the released iodine was titrated with 14.85 cm3 of a 0.1000 M Na2S2O3 solution. When ethanol reacts with K2CrO7, it is oxidized to acetic acid. Determine the mass fraction of ethanol.