Sciencemadness Discussion Board

Determine H2O2 % by density

Mateo_swe - 27-3-2022 at 09:36

So i measured my H2O2 to a density of 1.079g/ml.
According to included pdf it should be something like 22-23%.
It wasnt a very accurate measurement though, just a 100ml voulumetric flask and a pocket scale measuring grams with 2 decimals.

Is H2O2 % estimation by density somewhat accurate?
Or could this be off by very much?

I accidently got some drop on my thumb and got white marks that doesnt wash away so its some power left in it for sure.
This H2O2 has been outgassing unnormally much so i didnt think it was much % left, but it seems it got 22-23% if one can judge by density.
It was originally 35% but was outgassing much (a sign of some contamination), it even broke a cork and made one plastic bottle look like a balloon.
This was a year or 2 ago and it did stop outgas eventually and hasnt been touched since until now when i measured density.

Attachment: Determination of the densities of mixtures of Hydrogen Peroxide and Water - easton1952.pdf (481kB)
This file has been downloaded 61 times

B(a)P - 27-3-2022 at 14:00

Estimating density in this way can be accurate as long as the tools that you use to make measurements are accurate.
As you have alluded to the density calculation you performed is as accurate as the tools that you use to measure it, so long as your peroxide is pure. Assuming the contamination is at a low enough concentration that it does not significantly effect the density, the accuracy of the measurement will be as good as the accuracy of the volumetric flask and scale. Let's assume the scale is plus or minus 0.05 g and your flask plus or minus 0.2 mL.
So you can work out you uncertainty as follows.
You measured your volume as 100 mL so the true value could be between 99.8 and 100.2 mL and your measured mass 107.9 g is between 107.85 and 107.95 g. So your true density is between 1.081 and 1.078. With these errors we get basically the same answer as you had originally around 22 to 23%.
Use the actual error from your scale and volumetric flask and you will have your answer.

Mateo_swe - 27-3-2022 at 15:41

Perfect, thank you.

unionised - 28-3-2022 at 04:09

It also depends on there being no other impurities present.
For example, peroxide solutions are commonly acidified with H3PO4

maldi-tof - 29-3-2022 at 07:06

Or you just can titrate with some KMnO4 to get the exact concentration and see how accurate the value obtained via density it is.
Take into consideration as well that density changes with temperature.

katyushaslab - 7-4-2022 at 01:33

KMnO4 titrations aren't great for this unless you also factor in oxygen released by it also decomposing. MnO2 is cheaper and works the same :)

Sulaiman - 7-4-2022 at 08:54

I find it difficult to accurately determine the density of hydrogen peroxide solution
as bubbles form on the inside of my volumetric glassware,
causing apparent density to be less than actual.
This small error does not matter for my level of chemistry.

MnO2 seems to do a good job of decomposing hydrogen peroxide to measure oxygen volume.
P.S. my MnO2 was from dissected carbon/zinc batteries
the carbon does not affect the measurement as a mole of O2 is the same volume as a mole of CO2, if any is formed.

[Edited on 7-4-2022 by Sulaiman]

zed - 10-4-2022 at 23:05


unionised - 11-4-2022 at 01:19

Quote: Originally posted by zed  

With bubbles on.

Antiswat - 17-4-2022 at 10:59

whats the need for the very specific accuracy anyhow? besides science
if youre trying to volumetrically get some data with a catalyst i would advise you hammer the catalyst, MnO2 in this case into a hard pellet to limit reaction speed
or maybe glue it into a piece of metal tube with one end closed off