2 The balanced redox equation for the reactions is:- REDOX TITRATIONS (Unit 3 PPA 3)The aim of the experiment is to determine the mass of vitamin C in a tablet by carrying out a redox titration using a solution of iodine of accurately known concentration and starch solutions as an indicator.The balanced redox equation for the reactions is:-C6H8O I2 C6H6O H+(aq) I-(aq)(1) How many moles of iodine react with one mole of vitamin C (C6H8O6 )?(1) 1 mole of iodine.(2) What colour change indicates the end-point of the titration?(2) The appearance of apermanent blue- black colour.(3) Describe in detail how a vitamin C tablet can be dissolved to form exactly 250 cm3 of a vitamin C solution.(3) Place some distilled water (50 to 100cm3) in a beaker.Add a vitamin C tablet and stir until it has completely dissolved.Transfer the vitamin C solution from the beaker to a 250cm3 standard flask.Add distilled water to the standard flask until the solution is just below the mark on the stem of theflask.Add distilled water using a dropper until the bottom of the meniscus lies on top of the mark.Stopper the flask and shake to ensure the solution is thoroughly mixed.
3 Use the results to calculate the mass of vitamin C in the flask. 0.012.00.040 mol l-1iodine solution25 cm3 of vitamin C solution + starch indicator23.711.735.611.9The above results were obtained when a 25 cm3 sample taken from a standard flask containing 250 cm3 of vitamin C was titrated.Use the results to calculate the mass of vitamin C in the flask.Volume of iodine solution used = /2 = cm3.Number of moles of iodine used = 11.8/1000 x =So number of moles of vitamin C in 25 cm3 sample =So the number of moles of vitamin C in 250 cm3 flask =The mass of vitamin C present = no. of moles x gfm of Vitamin Cgfm of vitamin C (C6H8O6) = 176 gMass of vitamin C = x = g