Sciencemadness Discussion Board - Carbon + H2O2?

Carbon + H2O2?

jrmathis - 8-7-2008 at 00:06

I decided to see how h. peroxide would react with carbon lumps.
Upon addition of the H2O2, the mix began bubbling, I assume releasing O2.

After it was complete, there was no real change in the appearance of the mix.

Anyone know what happens here? (I don't entirely understand how to balance formulas as of yet.. :\ )

C + H2O2 --> ??

Thanks guys.

YT2095 - 8-7-2008 at 00:14

since it didn`t combust as H2O2 can do above a certain percentage, then the carbon just acted as a catalyst to speed up the decomposition that would occur naturally over time.

you`ll end with water, carbon (unchanged), and Oxygen as O2

in your formula you`ll only get 1 Oxygen atom, and Oxygen likes to be a molecule, so you`ll have to Double the amount of H2O2, making:

C + 2H2O2 ---> C + 2H2O + O2

jrmathis - 8-7-2008 at 00:19

ah ha! Thanks

woelen - 8-7-2008 at 00:43

YT, your equation is not valid. It is not correct to write the C in the equation, because it is arbitrary. The net equation is

2H2O2 --> 2H2O + O2

If I follow your analogy, then why would the equation with one C be correct. I can also write an equation with two C on both sides, with 10 C's or even this:

12345678C + 2H2O2 --> 12345678C + 2H2O + O2

If you want to write equations in which a catalyst is involved, then you can do that, but that requires insight in the mechanism of catalysis. A nice example is catalytic decomposition of H2O2 by iodide ion:

I(-) + H2O2 --> IO(-) + H2O

followed by

IO(-) + H2O2 --> I(-) + H2O + O2

You see? Here there is a mechanism, and the net effect is that H2O2 is decomposed and the iodide remains in solution.

Another nice example is catalytic oxidation by persulfate, with silver(I) ion as catalyst:

Ag(+) + S2O8(2-) --> Ag(3+) + 2SO4(2-)

Ag(3+) + 2e --> Ag(+)

The net reaction is S2O8(2-) + 2e --> 2SO4(2-). Without catalyst, this reaction is slow, but with the silver ion it is acting fast. You can oxidize e.g. manganese(II) to permanganate or chromium(III) to dichromate with this, and it only requires a little heating to 60 C or so. Without the silver these reactions do not occur, or they take soooooo looooong...

Formatik - 8-7-2008 at 02:59

Adding a few drops of about 90% peroxide onto charcoal lumps will also cause a decomposition reaction, but this is most likely due to impurities in the charcoal. Was it charcoal that you used or pure carbon?

ScienceSquirrel - 8-7-2008 at 03:01

You can oxidise carbon with hydrogen peroxide but it is a bit hazardous.
Acid Piranha ( a mixture of sulphuric acid and hydrogen peroxide ) will happily 'eat' black gunk but it can spontaneously explode and will detonate on contact with acetone etc.

YT2095 - 8-7-2008 at 03:08

it was based upon the idea that Carbon CAN react as I said in my post, that I figured it important to show that in his experiment using dilute H2O2 it didn`t react.

but I think Woelen is quite correct, it`s not needed to be shown Unless it reacts, such as:

C + 2H2O2 ---> 2H2O + CO2

Zinc - 8-7-2008 at 03:12

What are the ratios of 30% H2O2 and H2SO4 in the Piranha acid?

ScienceSquirrel - 8-7-2008 at 03:22

A brief introduction to Piranha.

The recipes are in the footnotes.

In my opinion this is not one to make at home. Read the account of the accident, one of the most terrifying lab mishaps I have ever heard of.
A lot of home chemists use drain cleaner sulphuric acid that contains various impurities, mixing it with hydrogen peroxide could be very nasty.

ScienceSquirrel - 8-7-2008 at 03:23

Oops I forgot the link

http://en.wikipedia.org/wiki/Piranha_solution

Formatik - 8-7-2008 at 03:51

For cleaning glassware, etc. I wouldn't use Pirahna on anything more than a few residues of carbon leftovers which can not be scraped off anymore. But other than that I've used it several times without problems. The acid mixture itself with 30% H2O2 is not explosive. Just keep it away from any fuels, as it gets very hot and releases gases.

[Edited on 8-7-2008 by Schockwave]

jrmathis - 8-7-2008 at 09:37

Quote:

Originally posted by SchockwaveWas it charcoal that you used or pure carbon?

It was pure carbon, in small lumps.
The H2O2 is only 3% drugstore variety.

To be honest, when I began adding H2O2, I didn't think anything would happen, and my curiosity peaked when something did happen.

Thanks for all the replies!

Formatik - 8-7-2008 at 17:23

Quote:

Originally posted by jrmathis

Quote:

Originally posted by SchockwaveWas it charcoal that you used or pure carbon?

Thanks for all the replies!

Ah, I see. I didn't think anything would happen with 90% either as it is unresponsive to a large number of substances unless there are catalysts in them, then it will decompose with bubble formation, etc.