Redox Titrations
I did a redox titration of NaBO3 with KMnO4. I used a .0545 M NaBO3 solution, and an average of .026 L of .01M KMnO4. I have to standardize the KMnO4 solution, does anyone know how to do this?
Write the equation and balance it.
Calculate moles NaBO3 used. That will be M x L NaBO3.
Using the coefficients in the balanced equation, convert moles NaBO3 to moles KMnO4, then,
M KMnO4 = moles KMnO4/L KMnO4.
Post your work if you get stuck.
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To standardize the KMnO4 solution, you need to determine its exact concentration. One way to do this is by titrating a known amount of a primary standard substance. In this case, you can use sodium oxalate (Na2C2O4) as a primary standard.
Here's how you can proceed with the standardization process:
1. Prepare a solution of sodium oxalate: Dissolve a weighed amount of sodium oxalate (around 0.2-0.3 g) in distilled water and transfer it to a clean flask. The precise weight should be recorded.
2. Add an indicator: Add a few drops of an indicator (such as phenolphthalein) to the flask. This indicator will help you determine the completion of the reaction during the titration.
3. Titrate with KMnO4: Using a burette, slowly add the KMnO4 solution to the sodium oxalate solution while stirring continuously. The reaction between sodium oxalate and KMnO4 can be represented by the following balanced equation:
5Na2C2O4 + 2KMnO4 + 8H2SO4 → 2MnSO4 + 10CO2 + 8H2O + 5Na2SO4
4. Observe the color change: The initial pink color of KMnO4 will fade as it reacts with sodium oxalate. As the reaction progresses, the solution will turn colorless.
5. Endpoint determination: Continue adding KMnO4 solution until you observe a permanent pink color that persists for 30 seconds. This indicates the endpoint of the titration, where all sodium oxalate has reacted with the KMnO4.
6. Record the volume used: Note the final volume of KMnO4 solution (recorded to the nearest 0.01 mL) that was required to reach the endpoint. Be cautious about parallax errors while reading the burette.
7. Calculate the concentration: Now, calculate the concentration of the KMnO4 solution using the stoichiometry of the reaction and the known weight of sodium oxalate. The formula is:
Concentration of KMnO4 (in mol/L) = (Weight of Na2C2O4 in grams / Molar mass of Na2C2O4) / Volume of KMnO4 used (in L)
Note: The molar mass of Na2C2O4 is 134.0 g/mol.
By following these steps, you can determine the exact concentration of your KMnO4 solution and standardize it for your redox titration experiment.