[bureto]

Hi, I came to this forum in hopes that I will be able to ask multiple questions in one post relating to this topic in mind. I have a couple of questions, mostly regarding the electrolysis of a sodium hydroxide solution. I have thought up a design for a electrolytic cell and I am curious if it will work.

1. As far as I know, stainless steel is resistant to corrosion due to an inert oxide layer formed by the other alloy metals. I am learning about redox reactions right now so I am no expert; but since stainless is not to be used as a anode, I am wondering why is it allowed as an cathode? Wouldn't the oxide layer be reduced, forming oxygen gas and thus exposing more of the metal and lead to corrosion?

2. I have also read that stainless forms hexavalent chromium when being used as a anode, so is that because it gains extra oxygen atoms due to the oxidizing process? If so, it should be okay to put it in a high oxygen environment, as long as no current is hooked up to it, right?

3. When using a carbon anode, does it only produce carbon dioxide? And is this gas formed from ions, or is there oxygen gas present first, which later reacts with the carbon?

4. Here is my design, I do not care at the moment that the gases are being mixed: https://imgur.com/a/xC4YD
My thoughts are that the increased surface area will increase the reaction rate. The only downside I can think of is that the gases mix, is there any other reason this cell wouldn't be very good? I have the graphite rods coming in the mail so I cannot test it but I am very curious to hear an experts criticism.

5. I plan on using sodium acetate as a salt in a future project, it produces carbon dioxide and hydroxide ions as some of the products. Similar to question three, is oxygen gas ever produced in this reaction?

In the future I would hope to have proper equipment and materials to build a cell like this one: http://woelen.homescience.net/science/chem/exps/precision_electrolysis/index_acetate.html Also if any of these questions are too broad to answer please let me know, in other forums such as stackexchange they didn't allow me to ask multiple questions but I really hope it is okay here.  I think it makes sense to make one post since it relates to the same topic!

[Elric82]

What are you seeking? Woelen is a good source. But, if you’re purpose is just Na metal, then there may be a better way than electrolysis.

[bureto]

Hi Elric,

I am mainly just seeking the gas as of right now. As far as I know, getting the sodium from the solution requires heating it up until it is molten and it's not really what I am after. I have a solar panel lying around and I thought it would be cool if I made some gas. I tested it with two prongs and it produced a considerable amount of gas, so now I am curious to see how efficient I can get it. Here is a good read I found: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392014000100012 I am taking a chemistry 12 course right now, but it gets boring as we do no experiments. I am hoping to have a little fun making this project.   

[billnotgatez]

@bureto
I am liking the experiment, but still trying to follow your logic.
Based on your links I see you are doing some good research.

At this point, I just want to confirm this one part of your logic

...
3. When using a carbon anode, does it only produce carbon dioxide? And is this gas formed from ions, or is there oxygen gas present first, which later reacts with the carbon?
...

I will come back to this thread when i have more time.

[bureto]

Hi bill,

thanks for taking interest in my project! Sorry about that, I forgot I was talking about a sodium hydroxide solution when writing that little bit, and I accidentally thought I was talking about a sodium acetate solution. I guess my mind wandered off a bit lol. I am still curious if it will produce any CO2, my best guess is no (maybe water is a stronger reducing agent hence the H2). Would oxygen gas ever react with graphite at close to standard conditions? I found this: http://www.oocities.org/capecanaveral/campus/5361/chlorate/graphite/indgra.html
which talks about it oxidizing,

"Vaaler 174 suggests that external attack of graphite anodes occurs by rapid adsorption of oxygen followed by a conversion to chemisorbed oxygen, which is then rapidly desorbed, breaking a carbon bond, to give carbon monoxide. Carbon monoxide is then mostly oxidised to carbon dioxide by dissolved oxygen or chlorine. "

It seems kind of old and also talks about chlorine being in the solution so I don't know if it will affect me. I guess I will have to wait and see what happens.   

[Borek]

getting the sodium from the solution requires heating it up until it is molten and it's not really what I am after.

Nope, you are confusing something, no idea what. You can't have sodium in the solution as it will immediately react with water (which is exactly why it is so difficult to produce it by electrolysis).

Melting sodium is rather trivial, as its melting point is around 100°C (almost the same as boiling water), so it is not a temperature difficult to get even in a primitive lab; the hard part is keeping the metal isolated from air and humidity to avoid vigorous reaction (which can be quite spectacular, if the scale is right https://www.youtube.com/watch?v=HY7mTCMvpEM&hd=1). Most obvious approach - keeping it under some inert liquid - is next to impossible, as sodium has a very low density and sinks only in very light liquids, which tend to be low boiling, volatile and flammable.

I understand making the sodium is not what you are aiming at, but being wrong here won't help you with whatever you plan to do.

[bureto]

Hi Borek,

Sorry about that, I'll make sure to do more research before I post here in the future. Thanks for the information!