Titration of KMnO4 and H2O2 under Acidic Conditions

In summary, during a redox titration involving Purple KMnO4 and H2O2, before the equivalence point is reached, the solution remains colorless and O2 gas is formed. The other options, such as the solution remaining purple and O2 or H2 gas forming, are not observed. This is due to the reduction potentials of H2O2 and MnO4- being strongly pH dependent, and in this low pH environment, another reaction takes place at 0.70V. Therefore, H2O2 cannot be solely responsible for the formation of H2O in this scenario.
  • #1
watermarked
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Homework Statement


A redox titration is carried out by adding Purple KMnO4 solution from a burette to a solution of H2O2 in a flask. Which of the following would occur in the flask before the equivalence point is reached?

The answer is: The solution is colorless and O2 is formed.
The other options were that the solution would remain purple and O2 gas would form, that the solution would remain purple and H2 gas would form, and the solution would be colourless and O2 gas would form.

Homework Equations


So my table says:
H2O2 + 2H+ + 2e- <=> 2 H20 has a reduction potential of +1.78
And Mn04 + 8H= + 5e- <=> Mn2+ + 4H20 has a reduction potential of +1.51

The Attempt at a Solution


Shouldn't H2O2 be the oxidizing agent, forming H2O?
 
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  • #2
First of all, potentials you listed are for standard conditions and they are strongly pH dependent. This titration takes place in a very low pH, have you tried to estimate formal potentials in the solution?

watermarked said:
Shouldn't H2O2 be the oxidizing agent, forming H2O?

And what would get oxidized in the process?

But the most important part is, there is another reaction taking place at 0.70V.
 
  • #3
No -- since the question only mentions that it takes place under "acidic conditions", I assumed it was under standard acidic concentrations. I guess that assumption was wrong, since it isn't one of the options.

Thanks for your help.
 

1. What is the purpose of titration of KMnO4 and H2O2 under acidic conditions?

The purpose of this titration is to determine the concentration of a solution containing KMnO4 (potassium permanganate) by using H2O2 (hydrogen peroxide) as the titrant. This can help in analyzing the oxidizing strength of KMnO4 and determining the unknown concentration of a substance in a sample.

2. What is the reaction taking place during this titration?

The reaction taking place is a redox reaction, where KMnO4 acts as the oxidizing agent and H2O2 acts as the reducing agent. The oxidation of H2O2 by KMnO4 causes a color change from purple to colorless, which can be used to determine the endpoint of the titration.

3. What are the necessary materials for this titration?

The necessary materials include a burette, a conical flask, KMnO4 solution, H2O2 solution, a standardized solution of FeSO4 (ferrous sulfate), and a suitable indicator such as potassium iodide (KI) or starch.

4. What are the steps involved in conducting this titration?

The steps involved are as follows: first, measure a fixed volume of the KMnO4 solution into the conical flask. Then, add a few drops of the indicator and titrate with the H2O2 solution until the color changes from purple to colorless. Record the burette reading and repeat the titration until consistent results are obtained. Finally, use the burette reading to calculate the concentration of KMnO4.

5. What are the possible sources of error in this titration?

Possible sources of error include inaccurate measurement of volumes, incorrect handling of the burette or conical flask, contamination of the solutions, and failure to properly identify the endpoint of the titration. It is important to use precise measurements and follow proper techniques to minimize these errors.

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