- Redox Titrimetric Analysis Of Ksfe C204 3 3h 0 Introduction Potassium Ferrioxalate Trihydrate K Fe C O 3h O Has Long 1 (64.72 KiB) Viewed 50 times
- Redox Titrimetric Analysis Of Ksfe C204 3 3h 0 Introduction Potassium Ferrioxalate Trihydrate K Fe C O 3h O Has Long 2 (80.12 KiB) Viewed 50 times
- Redox Titrimetric Analysis Of Ksfe C204 3 3h 0 Introduction Potassium Ferrioxalate Trihydrate K Fe C O 3h O Has Long 3 (61.39 KiB) Viewed 50 times
- Redox Titrimetric Analysis Of Ksfe C204 3 3h 0 Introduction Potassium Ferrioxalate Trihydrate K Fe C O 3h O Has Long 4 (66.89 KiB) Viewed 50 times
- Redox Titrimetric Analysis Of Ksfe C204 3 3h 0 Introduction Potassium Ferrioxalate Trihydrate K Fe C O 3h O Has Long 5 (72.46 KiB) Viewed 50 times
- Redox Titrimetric Analysis Of Ksfe C204 3 3h 0 Introduction Potassium Ferrioxalate Trihydrate K Fe C O 3h O Has Long 6 (72.46 KiB) Viewed 50 times
- Redox Titrimetric Analysis Of Ksfe C204 3 3h 0 Introduction Potassium Ferrioxalate Trihydrate K Fe C O 3h O Has Long 7 (63.34 KiB) Viewed 50 times
- Redox Titrimetric Analysis Of Ksfe C204 3 3h 0 Introduction Potassium Ferrioxalate Trihydrate K Fe C O 3h O Has Long 8 (71.93 KiB) Viewed 50 times
- Redox Titrimetric Analysis Of Ksfe C204 3 3h 0 Introduction Potassium Ferrioxalate Trihydrate K Fe C O 3h O Has Long 9 (36.2 KiB) Viewed 50 times
Given that Mno, is intensely purple in solution, and its reduction product Mn2 is colorless, the Mno, functions as its own indicator. When the purple MnO, is added from the buret to the oxalate solution, it is decolorized when it is completely reduced to Mnt? When all of the oxalate is consumed at the endpoint, the solution in the titration flask will be a light pink because of a slight excess of Mno The titration seems like a straightforward process, one that you are already very familiar with. However, one of the issues with using potassium permanganate is that it decomposes when exposed to light. We take precautions, such as storing the solid compound in opaque containers and solutions in brown glass bottles. Although this process is not too fast, one can never be quite sure what the concentration of KMnO, is based on the mass weighed out. Therefore, it is a common practice to standardize the KMnO, solution with another oxalate solution that is known to have a very accurately known concentration shortly before it is used. For example, an analytical lab who uses potassium permanganate on a regular basis would standardize their potassium permanganate solution once a week or every time a new batch was prepared. A good candidate for a standard solution is a compound that is high in molar mass (gives higher precision due to more sig figs when weighing it) and a compound that is highly stable under ambient conditions. We will be using sodium oxalate, Na,C,04, which fulfills these requirements. When you perform the lab you want to pay particular attention to accuracy and precision. This means, you need to record all values using correct number of significant figures and use a good technique when preparing solutions and during your titrations
Overview of Procedure Part One: Prepare oxalate solution (Na,C,0.) and calculate molarity. Part Two: Determine the concentration of permanganate solution (KMnO ) by titration (using the oxalate solution from Part One) Part Three: Titrate iron salt K Fe(C,04)3H,0 to determine percent purity of the sample. Now that you know the exact concentration of your permanganate solution, you can use it to titrate your iron salt and determine the oxalate concentration and it's percent purity. Procedure Part One: Preparation of a Standard Solution of sodium oxalate Na2C,04 In order to perform a quantitative analysis of our crystals, we must know the molarity of the titrant, KMnO, to at least three significant digits (4 sig figs would be better). Because of its high reactivity, it is not possible to prepare a standard solution of KMnO by direct weighing. Instead, we will prepare a standard solution of Na,co by direct weighing and use this solution to standardize (determine the exact concentration of the KMnO. solution The KMnO, solution is initially known to only approximate concentration of 0.02M. With your titration you will be able to determine its exact concentration to at least 3 significant figures. 1. Weigh out about 1 gram amount of pure, dry Na,C,0. you determined into a clean 100 mL beaker. 2. Record the exact mass in the data table in your lab notebook. 3. Add approximately 25-30 mL of distilled
4. Transfer the solution quantitatively to a 100.00 mL volumetric flask using several small rinses (10 mL or so) of the beaker with distilled water. Quantitative means that you don't want to lose a single Na,c,O molecule in the transfer. 5. Carefully add Di water to the calibration mark. Mix well by inverting the flask about 20 times. 6. Calculate the Molarity of this standard sodium oxalate solution. This is the M you will use in part two below to calculate the KMnO, molarity. Part Two: Standardization of KMnO, Solution The reaction of KMnO, with oxalate shown below is the reaction for the standardization, which is different from the reaction of KMnO, with Fe(C20.). This reaction requires a modest temperature of 70-75°C. Equ 2: 2 KMnO 4/39) + 6 H4 + 5 Na C,044) 8 H,0 + 2 Mn>*(aq) + 2 K + 10 Naam) + 10 CO2 (0) Note before you start: If the temperature is too high an unwanted side reaction (the formation of MnO, as an orange solid will appear) may occur. If your reaction turns orange while you are titrating, you will need to restart the trial. If your temperature was above 75°C make sure you turn down your hot plate. You can also add cold distilled water to cool down your solution. If your reactions turns orange after you finish the titration, it will not alter your results. 1. Pipet a 10.00 mL aliquot of the sodium oxalate solution into a 125 mL or 250 mL Erlenmeyer flask. 2. Using a graduated cylinder, add -10 mL of distilled water and -20 mL of 1 M H,SO. Note the approximate symbol!!! 3. Place the magnetic stir bar in the solution and set the flask upon the hot plate/stirrer and stir the solution at a moderate rate. Don't let it
4. Heat the solution to about 70°C. Make sure to not exceed 75°C, otherwise you might get some side reactions. Use a temperature probe to monitor the temperature and either lift up your flask or add distilled water if it starts getting too hot. 5. While you are waiting, obtain about 200 mL of KMnO, solution into a labeled clean, dry beaker. Rinse a buret and set it up with the KMnO, solution. Be sure to eliminate any air bubbles from the tip of the buret. 6. Once the oxalate solution is at temperature, slowly titrate it with KMnO. It will take a little for the solution to become colorless. You might want to start by adding 1-2 mL portions, then wait. Once you get close to the end point, you want to add the KMnO, drop by drop and wait for the KMnO, to be reduced to the colorless Mnt? Keep an eye on the temperature between 70- 75°C during the titration. Continue the addition of titrant until a permanent pink color is obtained. 7. Do a second and third titration using 10.00 ml aliquots of standard sodium oxalate following the same set of procedures. You should have 2 titrations that are within 0.1 mL of KMnO, solution added. Record all data and in data tables in your notebook Part Three: Analysis of K, Fe(0,0.),-34,0 In aqueous solution, the complex iron salt exists as the yellow green K Fe(C,0);-3H,0 am complex. In acidic solution, KMnOoxidizes the complex according to the net balanced equation below. Equ 3: 5 K Fe(C20.);•H,0 + 6 KMnO.+ 48 H 5 Fe3+ + 6 Mn2 + 30 CO, + 24 H,0 + 21 K* Note: The oxidation and reduction products are the same as in the standardization reaction. Feais +
4. Heat the solution to about 70°C. Make sure to not exceed 75°C, otherwise you might get some side reactions. Use a temperature probe to monitor the temperature and either lift up your flask or add distilled water if it starts getting too hot. 5. While you are waiting, obtain about 200 mL of KMnO, solution into a labeled clean, dry beaker. Rinse a buret and set it up with the KMnO, solution. Be sure to eliminate any air bubbles from the tip of the buret. 6. Once the oxalate solution is at temperature, slowly titrate it with KMnO. It will take a little for the solution to become colorless. You might want to start by adding 1-2 mL portions, then wait. Once you get close to the end point, you want to add the KMnO, drop by drop and wait for the KMnO, to be reduced to the colorless Mnt? Keep an eye on the temperature between 70- 75°C during the titration. Continue the addition of titrant until a permanent pink color is obtained. 7. Do a second and third titration using 10.00 ml aliquots of standard sodium oxalate following the same set of procedures. You should have 2 titrations that are within 0.1 mL of KMnO, solution added. Record all data and in data tables in your notebook Part Three: Analysis of K, Fe(0,0.),-34,0 In aqueous solution, the complex iron salt exists as the yellow green K Fe(C,0);-3H,0 am complex. In acidic solution, KMnOoxidizes the complex according to the net balanced equation below. Equ 3: 5 K Fe(C20.);•H,0 + 6 KMnO.+ 48 H 5 Fe3+ + 6 Mn2 + 30 CO, + 24 H,0 + 21 K* Note: The oxidation and reduction products are the same as in the standardization reaction. Feais +
Analysis and Calculations The purpose of this experiment is to determine the percent purity of K,Fe(CO).•3H,0. Throughout your calculations pay attention to accuracy and precision. Make sure you use the appropriate number of significant figures. The glassware and techniques used are all geared towards obtaining high accuracy and precision. Clearly present all data and results; include correct units and label everything clearly so it is easy to follow. Show all calculations clearly and in an organized fashion. Based on the data you have collected in this lab, report the following: 1. Determine the molarity of the Na,C,04 solution you prepared in part 1 based on the amount of sodium oxalate weighed out. Clearly indicate this answer. 2. Determine the molarity of the standardized KMnO, solution you analyzed in part 2 . Make sure to average your data and eliminate any outlying data 3. Determine the percent purity of KsFe(C,0)3-3H,0 you analyzed in part 3 by following these steps: a. Calculate the concentration (molarity) of K Fe(C,0), 3H,0 based on the titration data and equation 3. Clearly report this result b. Now calculate the theoretical concentration (molarity) of KsFe(C,0.):3H,0 based on the mass weighed out and dissolved in the 100.00 ml flask. This is the molarity if the sample was 100% pure. Clearly report this result. c. Finally, the percent purity is: Your answer should be a value between 50- 100%. Clearly indicate this answer.
(2) Calculate the known M of Na2C204 used to standardize the KMnO4. (This is Part One) (3) Using the known M of Na2C204 from Part One, the titration data, and the reaction stoichiometry, calculate the M of KMnO4 (Part Two). (4) Using the calculated M of KMnO4 (that you just found from Part Two), the titration data, and the reaction stoichiometry calculate the experimetal M of K3Fe(C204)3 : 3H20. (This is the Part Three titration) (5) Using the mass of K3Fe(C204)3. 3H20 and the known total volume of solution that was made calculate the expected Molarity of K3Fe(C204)3 : 3H20. The % purity is the experimental M/expected M (then x 100 of course for percent.) (6) Organize your calculations and result tables and write a conclusion.
Data Percent Purity of K Fe(CO):3H.0 Part One Preparation of Sodium Oxalate Making Na CO solution Mass of Na.C.O. (g) 1.055 Part Two Standardization of KMnO4 There are two trials for the volumetric analysis. Do the calculations for each trial separately then average the data. Initial buret reading (mL) 0.20 17.133.2 Final buret reading (ml) 17.133.249.6 Part Three Analysis of K.Fe(CO), 3HO Making K Fe(CO): 3H0 analyte solution Mass of K,Fe(C,0)- 34,0 1.0068 There are three trials for the titration. Do the calculations for each trial separately then average the data. Titrating K Fe(CO):3H0 with KMnO Trial Trial 2 Trial 3 Initial buret reading (ml)0,60 11.120.8 Final buret reading (mL) 10.7 20.8 30.5