STANDARDIZATION of KMnO4
1) Dissolve 1.67 g of KMn04 in 500 ml of distilled water and stir well until dissolved. Be sure that all KMn04 has dissolved.
2) Weigh out duplicate 0.2 g previously dried standard Na2C204 and dissolve in ~200- ml of H2O + 30- ml of 6N H2SO4.
3) Add 20- ml of KMnO4 to the solution rapidly from the burette with stirring. The solution will become purple. Let it stand for a few minutes and color should disappear. If a brown color forms and persists it indicates that too much KMnO4 has been added, and MnO2 has formed. Start over and add lesser amount of KMnO4.
4) Now, heat solution to 55-60o C and complete titration at that temperature adding KMn04 dropwise until a faint pink remains for at least 15 sec.
5) Calculate the molarity of KMnO4.
1) Weigh 0,25 g iron ore ( to 0.1 mg precision)
2) Add 20 ml of conc.HCl and heat on hot plate
3)Add equal amount of distilled water
4) Add ~7-9 drops of SnCl2 solution dropwise until yellow Fe+3 color has just disappeared (color changes from orange yellow to greenish yellow (Fe2+). Place solution on white paper to observe the color.
5) Cool the solution to room temperature and add at once ~10- ml HgCl2. A slight light ppt. of Hg2CI2 should form. If no ppt. or a gray/black ppt. is formed, discard sample and start over.
6) Allow the solution to stand for 2-3 minutes, then add about 300- ml H2O + 25ml Reinhardt's solution.
7) Rinse the burette with KMnO4 and titrate dropwise until a definite faint pink color is obtained. Too rapid addition of KMnO4 results in high results. Since Fe+3 air oxidizes slowly, the samples should be reduced and titrated one at a time.
NOTE: in order to clean up KMnO4, spill NaHSO3 solution.
Trial 1 Trial 2
wt. of Na2C2O4 __________g __________g
vol. of KMnO4 __________ __________
molarity of KMnO4 __________ __________
avg. normality of KMnO4 ______________
avg. molarity of KMnO4 ______________
volume of unknown sample __________ml __________ml
vol. of KMnO4 __________ml __________ml
Normality of Fe2+ __________ __________
AVG Normality of Fe2+ ______________
AVG Molarity of Fe2+ ______________