Part One: Preparation of a Standard Solution of sodium oxalate Na₂C₂O₄

In order to perform a quantitative analysis of our crystals, we must know the molarity of the titrant, KMnO₄, 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 KMnO₄ by direct weighing. Instead, we will prepare a standard solution of Na₂C₂O₄ by direct weighing and use this solution to standardize (determine the exact concentration of) the KMnO₄ solution.

The KMnO₄ 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 Na₂C₂O₄ 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 water to dissolve the sample completely.

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 dont want to lose a single Na₂C₂O₄ 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 KMnO₄molarity.

Data Experiment 2 Percent Purity of K3Fe(C204)3 3H20 Part One Preparation of Sodium Oxalate Making Na2C204 solution Mass of Na2C204 (g) 1.055 Part Two Standardization of KMnO4 Shading There are two trials for the volumetric analysis. Do the calculations for each trial separately then average the data. Initial buret reading (mL) Initial buret reading (mL) 0.20 17.1 17.1 33.2 33.2 49.6 Part Three Analysis of K3Fe(C204)3 3H2O Making KzFe(C204)3 3H20 analyte solution Mass of KzFe(C2O4)3 3H20 1.006 g There are three trials for the titration. Do the calculations for each trial separately then average the data. Titrating K3Fe(C2O4)3 3H20 with KMnO4 Trial 1 Trial 2 Trial 3 0.60 11.1 20.8 Initial buret reading (mL) Final buret reading (mL) 10.7 20.8 30.5