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This experiment explores the use of acidified potassium permanganate as a strong oxidizing agent in titration. The objective is to determine the percentage by mass of oxalate ions in a sample of iron (II) oxalate. Acidified potassium permanganate is added to acidified iron (II) oxalate, resulting in a series of redox reactions. The change in color of the solution during the titration process is used to determine the endpoint. Theoretical and experimental calculations are performed to determine the accuracy of the results.
Acidified potassium permanganate is a potent oxidizing agent capable of oxidizing various substances while reducing itself in the process.
It undergoes the following redox reaction:
Both iron (II) and oxalate ions can be oxidized when they come into contact with an oxidizing agent, leading to the following reactions:
2. Fe2+ → Fe3+ + e-
(Yellow) → (Colorless)
When potassium permanganate is added to acidified iron (II) oxalate, two redox reactions occur:
2. 5Fe2+ + MnO4- + 8H+ → Mn2+ + 4H2O + 5Fe3+
The color changes of the solution during the titration are as follows: initially, the solution is pale green due to the presence of iron (II) ions.
After the addition of potassium permanganate, it turns yellow due to the formation of iron (III) ions. Finally, the solution changes from yellow to purple after the addition of excess potassium permanganate, indicating the absence of reducing agents to react with the permanganate ions.
Trial | Final Reading (cm3) | Initial Reading (cm3) | Volume of KMnO4 Used (cm3) |
---|---|---|---|
1 | 29.9 | 2.6 | 27.3 |
2 | 29.0 | 1.7 | 27.3 |
3 | 29.9 | 2.5 | 27.4 |
4 | 29.4 | 2.0 | 27.4 |
Average volume of KMnO4 used = (27.3 + 27.4 + 27.4) / 3 = 27.367 cm3
Number of moles of KMnO4 used = (27.367 / 1000) * 0.02 = 5.473 × 10-4 moles
For every 3 moles of MnO4- used, 5 moles of FeC2O4.2H2O is reacted.
No. of moles of FeC2O4.2H2O in every 25 cm3 = 5.473 × 10-4 / 3 * 5 = 9.122 × 10-4 moles
There are also 9.122 × 10-4 moles of oxalate in every 25 cm3. Then there would be 9.122 × 10-3 moles of oxalate in 250 cm3 of the solution.
Weight of C2O42- in the sample = 9.122 × 10-3 * (12 * 2 + 16 * 4) = 0.803g
Percentage by mass of C2O42- in the sample (found by experiment) = (0.803 / 1.782) * 100% = 45.04%
Molar mass of FeC2O4.2H2O as written on its bottle = 179.9 g/mole
Percentage by mass of C2O42- in the sample (theoretically) = (24 + 16 * 4) / 179.9 * 100% = 48.92%
The experiment determined that the percentage by mass of C2O42- ions in the sample of iron (II) oxalate was found to be 45.04%, while the theoretical percentage was calculated to be 48.92%. The variation between the experimental and theoretical values may be attributed to experimental error and incomplete reaction kinetics.
To improve the accuracy of the experiment, careful pipetting and more precise temperature control during heating should be emphasized. Additionally, consideration could be given to exploring alternative methods for accelerating the reaction between oxalate and permanganate ions to reduce the overall duration of the experiment.
Acidified Potassium Permanganate Titration Lab Report. (2017, Aug 11). Retrieved from https://studymoose.com/document/determination-of-the-percentage-of-oxalate-in-ironii-oxalate-by-redox-titration
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