Oxidation-Reduction Titration
Advanced Chemistry Lab #3
Rachel Metzler
11/16/10
Purpose: The purpose is to, through use of titration and then stochiometric
calculations, to find the concentration of the Potassium permanganate and then to
find the concentration of the Oxalic acid.
Procedure: Using standard titration methods, titrate first Fe2+ combined with H2SO4
till it turns a very light pink using MnO4. Then titrate with MnO4 the H2C2O4 with
MnSO4 introduced to act as a catalyst. Using this data determine the molarity of the
MnO4 and then the H2C2O4.
Pre-Lab Questions:
1. Write the balanced net ionic equation for the reaction between MnO4- ions
and H2C2O4 in acid solution. MnO4- + H2C2O4 
2. How many moles of Fe2+ ions can be oxidized by 0.043 moles of MnO4- ions?
3. 1.630 g of iron ore is dissolved in an acidic solution. This solution is titrated
to a pink endpoint with 27.15 mL of a 0.020 M KMnO4 solution.
a. How many moles of MnO4- ions were consumed?
b. How many moles of Fe2+ were in the iron ore sample?
Results:
c. What is the percent of iron in the iron ore sample?
Observations: (General descriptions of visible appearances or changes that occur
during the experiment, such as “table salt is a white, cube-shaped crystal which dissolves
in water. (Qualitative))
Data:
Part 1
Molarity of Fe2+ ____.1____ M
Trial 1
Trial 2
Trial 3
Volume of Fe2+ solution titrated
10
10
10
Initial volume of MnO4- solution
4.45
5.59
4.17
Final volume of MnO4- solution
22.9
18.98
16.69
Volume of MnO4- added
18.45
13.3
12.52
1
Part 2
Molarity of MnO4- solution _____.02_______M
Trial 1
Trial 2
Volume of H2C2O4 solution titrated
25
25
Initial volume of MnO4- solution
16.69
31.90
Final volume of MnO4- solution
31.90
47.61
Volume of MnO4- added
15.21
15.71
Molarity of H2C2O4 solution _______.025_____M
Calculations:
Part 1: 22.9-4.45=18.45, 18.89-5.59=13.3, 16.69-4.17=12.52
Part 2: 31.9-16.69=15.21, 47.61-31.90=15.71
5 fe: 1 MnO4
5(.1x10) = 1(Mx14.76)  5/14.76 = .34
Conclusion: Through this lab, titration and stoichiometry, the molarity of potassium
permanganate and oxalic acid is found.
Discussion of Theory: In this lab, the theory of titration is demonstrated. Through
using a known solution with a unknown molarity you can then titrate another
known solution (with known molarity and volume) to a specific volume. Using this
titrated volume you can find the molarity.
Experimental Sources of Error: (What are some specific sources of error, and how do
they influence the data? Do they make the values obtained larger or smaller than they
should be? Which measurement was the least precise? Instrumental error and human
error exist in all experiments, and should not be mentioned as a source of error unless
they caused a significant fault. Significant digits and mistakes in calculations are NOT a
valid source of error. In writing this section it is sometimes helpful to ask yourself what
you would do differently if you were to repeat the experiment and wanted to obtain better
precision. If you can calculate percent error, do so and include in this section. )
Post Lab Questions: (Answer any questions included in the lab. Answer in such a way
that the meaning of the question is obvious in your answer. )
2
1. From the Part 1 standardization data, calculate the molarity of the MnO4solution for each trial. Average the values and enter the average in the Part 2
Data Table.
2. From the Part 2 titration data, calculate the molarity of the H2C2O4 solution
for each trial. Average the values and enter the average in the Part 2 Data
Table.
3. How many moles of Fe2+ ions and MnO4- ions were titrated in each Part 1
trial?
4. How many moles of oxalic acid, H2C2O4 were titrated in each Part 2 trial?
3