Answer Happy

Experiment 3. Quantitative determination of total Fe in an iron ore sample solution (1) The precisely measured weight of 0.5 g of an iron ore (hematite, Fe₂O3) was 0.5015 g. It was decomposed with HC1 (2+1) by heating, and the undissolved residue was filtered. The resultant filtrate was diluted to 200 mL, which was used as a sample solution. Calculate the approximate concentration (mol L-¹) of Fe in this sample solution (suppose that hematite does not contain metal impurities other than Fe). Concentration of Fe in the sample solution mol L-¹ (2) 20 mL of this sample solution was put in a conical beaker with a volumetric pipette and heated to 90°C to 95°C, tin(II) chloride was dropped until the solution turned slightly light yellow, and then an indigocarmine solution was added to change the color from yellow-green to blue. Until the blue disappeared, a titanium(III) chloride solution was dropped in while stirring the sample solution. Immediately after that, a K₂Cr₂O, solution was dropped in until the solution developed a blue color for 5 seconds. 20 mL of mixed acid (sulfuric acid, phosphoric acid, and water mixed at a ratio of 3:3:14) was added to this solution, and then it was diluted with water to 100 mL. 0.5 mL of sodium diphenylamine sulfonate indicator was added, and titration was performed with the 8.3 x 10³ mol L¹ K₂Cr₂O₂. Calculate the approximate titration value (mL) needed to reach the end point. Titration value of the 8.3 × 10³ mol L¹K₂Cr₂O7 solution about mL