0730. Solving a chemistry problem

2. Quantitative determination of glucose in the substance by iodimetry is carried out according to the following procedure: about 0.1 g (exactly weighed) of the glucose substance is placed in a 50 ml volumetric flask (solution A). 5 ml of solution A is transferred to a titration flask, 5 ml of 0.1 mol/l iodine solution (I2) and 7.5 ml of 0.1 mol/l sodium hydroxide (NaOH) solution are added. The flask is closed and left for 20 minutes in a dark place. After the specified time, 5 ml of dilute sulfuric acid (H2SO4) is added to the flask and titrated with 0.1 mol/l sodium thiosulfate solution (Na2S2O3). The indicator is starch. At the same time, a control experiment is carried out.
Calculate the quantitative content and evaluate the quality of the substance dextrose (glucose) by quantitative content, if 3.5 ml of 0.1 mol/l sodium thiosulfate solution with Kp = 1.01 was used to titrate a 0.1025 g sample. The control experiment used 4.7 ml of 0.1 mol/l sodium thiosulfate solution. 1 ml of 0.1 mol/l sodium thiosulfate solution corresponds to 0.009985 g of dextrose, which should be in the substance. not less than 98.5%.