Sciencemadness Discussion Board

H2O2 Decomp to O2 - Volume Calc?

Capt Chaos - 12-2-2012 at 18:58

Okay, I'm tired and need a peer review/conflict resolution.
What did I do wrong below?:(
40 volume peroxide is only supposed to produce 40 x 250ml = 10 L, not 21. I've even done the experiment and it's more like 10 L (maybe a little less). Definitely not 21 L.
It's probably something obvious but I'm bleary. Have to iron this out tomorrow, so would love some input. I'll revisit tomorrow.

H2O2+KI=O2(800x600).jpg - 187kB

Poppy - 12-2-2012 at 19:19

It's by definition, the volume of oxygen gas the peroxide would release if decomposed completly at room temperature. Thus 40 volumes would mean a 250mL bottle would release 40x250mL oxygen gas, thats 10L <_<

Neil - 12-2-2012 at 20:46

Looks like you mixed up O and O2 --> ~20L of O vs ~10L O2

Capt Chaos - 13-2-2012 at 03:45

Quote: Originally posted by Neil  
Looks like you mixed up O and O2 --> ~20L of O vs ~10L O2


I am not sure I follow.

O2 is the correct in the formula and most of the references are fairly clear, stating that the volume rating is based on oxygen (O2).

It would seem unusual to assign a volume to just 'O'. Would O have a volume in this context and if it did, would it be likely to be half of O2?

unionised - 13-2-2012 at 11:15

Quote: Originally posted by Poppy  
It's by definition, the volume of oxygen gas the peroxide would release if decomposed completly at room temperature. Thus 40 volumes would mean a 250mL bottle would release 40x250mL oxygen gas, thats 10L <_<


No it isn't.
It's the volume you get if you add it to excess of an oxidant - typically KMnO4.
That way you get twice as much oxygen given off so your product looks twice as good.