Oxidation-Reduction Titration Rachel Metzler

Oxidation-Reduction Titration Rachel Metzler Advanced Chemistry Lab #3

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.

2+ Procedure: Using standard titration methods, titrate first Fe 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+ - 2. How many moles of Fe 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? c. What is the percent of iron in the iron ore sample? Results:

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 MnO4 solution 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. 2+ - 3. How many moles of Fe 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?