# [Chemistry] Determine the concentration of h2o2 by redox titration

• Kevlarji
In summary, two experiments can be used to determine the exact concentration of H2O2 in a solution of approximately '100-volume'. One involves a redox titration with potassium manganate (VII) and the other does not. The end point of the titration is noted by a pale pink color and no indicator is required as the solution turns pale pink once all the H2O2 has reacted. The meaning of '100-volume' is that one volume of H2O2 releases 100 volumes of oxygen when catalytically decomposed. The second experiment can involve using a catalyst such as MnO2, blood, or cigarette ash to measure the volume of oxygen evolved from a known volume of solution. In order to
Kevlarji

## Homework Statement

You are provided with a solution of hydrogen peroxide which is known to be approximately ‘100-volume’. Plan two experiments that would enable you to determine the exact concentration of H2O2 in mol dm-3, in this solution. One of your experiments should involve a redox titration with potassium manganate (VII). The other experiment should not involve a titration.

## Homework Equations

2KMnO4 (aq) + 5H2O2 (aq) + 3H2SO4 (aq) --> 2MnSO4 (aq) + K2SO4 (aq) +5O2 (g) + 8H2O (l).

2H2O2 --> 2H2O + O2

3. My questions

Why is KMnO4 it's own indicator?

What is meant by 100-Volume and how can i put it into context?

What catalyses the disproportionation of h2o2?

4. The attempt at a solution

The end point of this reaction is noted by a pale pink colour. No indicator is required as the solution goes pale pink once all of the H2O2 has reacted. I know this has something to do with the redox chemistry but I am not exactly sure.

100-Volume one i believe this means one volume of h2o2 realeses 100 volumes of oxygen when catalytically decomposed. what does it mean by volume? And how can i use this to determine conc of h2o2 as the second experiment.

Liver?

Last edited:
Kevlarji said:
The end point of this reaction is noted by a pale pink colour. No indicator is required as the solution goes pale pink once all of the H2O2 has reacted. I know this has something to do with the redox chemistry but I am not exactly sure.

http://www.titrations.info/potentiometric-titration

No special chemistry involved - once you add excess of permanganate, its strong color is well visible in the solution.

100-Volume one i believe this means one volume of h2o2 realeses 100 volumes of oxygen when catalytically decomposed. what does it mean by volume?

Not sure what what you are asking about. 1 mL of solution gives 100 mL of gas.

And how can i use this to determine conc of h2o2 as the second experiment.

Start with known volume of solution, measure volume of gas evolved. MnO2 is a good catalyst, drop of blood will do the trick too, and I think cigarette ash is quite efficient at decomposing hydrogen peroxide as well, not too sure about the last one.

Hi Borek, I was wondering if you could help me. I'm doing the titration of H2O2 with KMnO4 in order to determine the concentration of H2O2. I understand that H2SO4 is required in the reaction, now if I dissolve the KMnO4 in H2SO4 does that count? Also, if I dissolve 2.5g of solid KMnO4 in 47.5cm3 of H2SO4. Will this be the resulting concentration?
2.5/ 50 = 0.05 mol dm-3.

Also, if I dissolve the KMnO4 in the acid, the number of moles of H2SO4 as required in the reaction (3) will not exist will it because the KMnO4 and the H2SO4 have been combined?

I appreciate any help! thank you!

mememe91 said:
I understand that H2SO4 is required in the reaction, now if I dissolve the KMnO4 in H2SO4 does that count?

No idea what you mean. If you dissolve permanganate in sulfuric acid you get strong oxidizing mixture.

Also, if I dissolve 2.5g of solid KMnO4 in 47.5cm3 of H2SO4. Will this be the resulting concentration?
2.5/ 50 = 0.05 mol dm-3.

Why do you think final volume will be 50 mL? I am almost sure it won't.

Also, if I dissolve the KMnO4 in the acid, the number of moles of H2SO4 as required in the reaction (3) will not exist will it because the KMnO4 and the H2SO4 have been combined?

Same problem as above - no idea what you mean. You have mixed these things, that's OK. Why do you think they don't exist any more?

I'm sorry, I'm really confused! How would I make a solution of KMnO4 of concentration 0.05 mol dm-3 by dissolving the manganate in H2SO4? How much H2SO4 would I need?

mememe91 said:
I'm sorry, I'm really confused! How would I make a solution of KMnO4 of concentration 0.05 mol dm-3 by dissolving the manganate in H2SO4? How much H2SO4 would I need?

Take correct amount of permanganate, dissolve in smaller volume of acid, once it is dissolved - fill up to 50 mL. Voumes are not additive and it is very difficult to predict what voume of acid you will need. You can do it sometimes having density tables.

## 1. What is redox titration?

Redox titration is a type of chemical analysis method used to determine the concentration of a substance, in this case hydrogen peroxide (H2O2), by measuring the transfer of electrons between two reactants. This method involves using a known concentration of a titrant, typically a strong oxidizing or reducing agent, to react with the substance being analyzed.

## 2. Why is redox titration used to determine the concentration of H2O2?

Redox titration is used to determine the concentration of H2O2 because it is a very sensitive and accurate method. It allows for the direct measurement of the analyte, in this case H2O2, without the need for any complex calculations or equipment. Additionally, redox titration can be performed relatively quickly and is a cost-effective method of analysis.

## 3. What is the principle behind redox titration?

The principle behind redox titration is based on the transfer of electrons between two substances. In this case, the titrant, which is a known concentration of an oxidizing or reducing agent, will transfer a certain number of electrons to the analyte, H2O2, until the reaction reaches completion. By measuring the amount of titrant used, the concentration of H2O2 can be calculated.

## 4. How is the concentration of H2O2 calculated using redox titration?

The concentration of H2O2 is calculated using the titration formula: C1V1 = C2V2, where C1 is the concentration of the titrant, V1 is the volume of titrant used, C2 is the concentration of H2O2, and V2 is the volume of H2O2 being analyzed. By plugging in the known values and solving for C2, the concentration of H2O2 can be determined.

## 5. What are some common titrants used in redox titration for determining the concentration of H2O2?

Some common titrants used in redox titration for determining the concentration of H2O2 include potassium permanganate (KMnO4), potassium dichromate (K2Cr2O7), and iodine (I2). These substances are strong oxidizing agents and react with H2O2 in a known ratio, making them ideal for this type of analysis.

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