Lab 4: Titration of a Redox Reaction The purpose of this experiment is to standardize a solution of Mohr’s salt, and to use titration to determine the volume ration of ferrous solution to the permanganate standard and calculate the concentration of the ferrous solution. First, Mohr’s salt was mixed with H2S04. Then, the solution was titrated until the end point was reached. The volumes were recorded, and used to calculate the molarity of the ferrous solution. The major findings in this lab were that titration in a redox reaction an be used to find the concentration of one solution if the other one is given.Order now
This lab’s significance is that it shows the proper way to calculate molarities using titrations. The major conclusions show that molarity of an unknown substance can be reached by titrating it with another substance, with a known molarity. Purpose: To standardize a solution of Mohr’s salt. To use titration to determine the volume ratio of ferrous solution to the permanganate standard and to calculate the concentration of the ferrous solution. Materials: . 020M potassium permanganate solution
Mohr’s salt solution (concentration unknown) 10- mL volumetric pipet Pipet bulb Beakers Procdure: Get 40 mL of standardized Potassium Permanganate and Mohr’s Salt solutions. Rinse the burets, and record the initial volumes. Measure 10mL of Mohr’s Salt solution. Add 10 mL of H2S04 solution. Begin titrating with the Potassium Permanganate until the endpoint is reached. Record the final volumes. Discard the liquid, and do the titrations 2 more times. Record the volumes like the first time. Data: Amount of Fe2+ (mL) Initial amount (mL) (mL) Trial 1 10. 0 19. 5 29. 12 10. 08 Trial 2 10. 00 29. 12 39. 33 10. 21 Trial 3 10. 00 39. 33 49. 54 10. 21 Calculations: I . 5 (Fe2+ Fe3+ + e-) MI-1041- + 8H+ + -+ Mri2+ + 4H20 Final amount (mL) Amount Change MI-1041- + 5Fe2+ + 8H+ -+ Mri2+ + 5Fe3+ + 4H20 2. 10. 08 rnL+ 10. 21 rnL+ 10. 21 mL = average 10. 17 mL0fKMn04 3 10 mL+ 10 mL+ 10 mL = average 10 mL of Fe2+ 3. 10. 17 mL KMn04* . 020 mol KMn04* 1 mol Mri04 1000 mL KMn04 1 mol KMn04 . 000203 mol Mri04 4. 1 mol MI-1041- : 5 mol Fe2+ , and there are . 000203 mol Mri04 , so . 000203 mol MI-1041- * 5 mol Fe2+= . 0102 mol Fe2+ . .00102 mol Fe2+= . 1017M . 01 L 6. Molar mass of ferrous ammonium sulfate hexahydrate is 302. 07g 39. 21 g Mohr’s salt* 1 mol Mohr’s salt * = . 1298M 302. 07 g Mohr’s salt IL 7. (. 1298- 21. 65% error . 1298 Error Analysis: the pipet unnoticed, making the permanganate use seem more than it was supposed to be, increasing the final solution. Another source of error could be the spilling of some of the Mohr’s salt solution. This would increase the final molarity, because the solution would seem more concentrated.
If I could redo the experiment, I would atch carefully at the solutions, making sure no more or less was being used. Conclusions: From this experiment, I conclude that titrations are a valid way of determining the molarity of an unknown substance, because you can accurately calculate the molarity using another substance of a known molarity. I also discovered that an acid- base titration has different mole ratios that a redox titration. Discussion: 1. a. Permanganate was a purple color. b. H2S04 was a lighter purple color. c. Ferrous was greenish- yellow. d. Manganese was pink. The indicator was 2.