Decomposition of Sodium Carbonate: Examining the Reaction with Water

[Jadaav]

Does sodium reacting with water produces sodium hydroxide directly or produces sodium oxide first then hydroxide ?

 

[Borek]

No place for oxide.

You can think about the reaction as if HOH was an acid.

 

[Jadaav]

So you mean that Sodium reacting with water becomes Sodium Hydroxide directly ?

Then how is Sodium Oxide produced ?

 

[Bloodthunder]

2 NaOH + 2 Na → 2 Na2O + H2
Na2O2 + 2 Na → 2 Na2O
2 NaNO2 + 6 Na → 4 Na2O + N2

OR

6 Na + 2 O2 → 2 Na2O + Na2O2

 

[Borek]

Simplest method - roasting sodium carbonate.

 

[Jadaav]

Thanks:)

Does Sodium reacting with Steam produces Sodium hydroxide ? I mean the metals above Magnesium can react with steam to form metal oxide or hydroxide ?

 

[lightarrow]

Simplest method - roasting sodium carbonate.

I don't think you can get sodium oxide in that way.

 

[Borek]

I don't think you can get sodium oxide in that way.

Most carbonates decompose in high temperatures yielding CO₂ and metal oxides, sodium carbonate is not different. It is just a matter of temperature applied. From what I remember, standard Bunsen burner should be enough to heat the carbonate high enough.

 

[chemisttree]

I don't think you can get sodium oxide in that way.

Yes, that will do it. You can also roast sodium hydroxide.

 

[Jadaav]

Thanks:)

Does Sodium reacting with Steam produces Sodium hydroxide ? I mean the metals above Magnesium can react with steam to form metal oxide or hydroxide ?

Answer please!

 

[Borek]

Depends on the steam temperature. If it is low, you will get NaOH. If it is hot enough, you should get Na₂, this is not much different from, the roasting.

I have never seen roasted NaOH. It easily melts and can splash, making the experiment much more dangerous. I remember roasting carbonates.

 

[Jadaav]

OK, that was really helpful. Thanks:)

 

[lightarrow]

Most carbonates decompose in high temperatures yielding CO₂ and metal oxides, sodium carbonate is not different. It is just a matter of temperature applied. From what I remember, standard Bunsen burner should be enough to heat the carbonate high enough.

I'm confused, because here, for example, they say something different:

http://www.practicalchemistry.org/experiments/thermal-decomposition-of-metal-carbonates,281,EX.html
<<Students should find that sodium and potassium carbonates give no carbon dioxide or any other sign that decomposition has taken place, even after prolonged heating.>>

http://www.chemguide.co.uk/inorganic/group1/compounds.html
<<Heating the carbonates

Most carbonates tend to decompose on heating to give the metal oxide and carbon dioxde.
For example, a typical Group 2 carbonate like calcium carbonate decomposes like this:
CaCO₃ --> CaO + CO₂
In Group 1, lithium carbonate behaves in the same way - producing lithium oxide and carbon dioxide:
Li₂CO₃ --> Li₂O + CO₂
The rest of the Group 1 carbonates don't decompose at Bunsen temperatures, although at higher temperatures they will.>>

 

[Borek]

The rest of the Group 1 carbonates don't decompose at Bunsen temperatures, although at higher temperatures they will.>>

That could be easy to check if someone has access to thermogravimetric curves for these carbonates. I am limited to what I can google, first one that I found

http://www.muhlenberg.edu/depts/chemistry/webmaps/sodacarb.htm

shows that sodium carbonate doesn't decompose up to 800 deg C, but Bunsen goes higher. Google finds also this paper: http://www.tandfonline.com/doi/abs/10.1080/00986440108912851#preview. It can't be read without paying, but google shows quote from the paper:

TGA curve of anhydrous sodium carbonate shows weight loss at the temperature range of 900–1175 K under static air atmosphere [9].

 

[lightarrow]

That could be easy to check if someone has access to thermogravimetric curves for these carbonates. I am limited to what I can google, first one that I found

http://www.muhlenberg.edu/depts/chemistry/webmaps/sodacarb.htm

shows that sodium carbonate doesn't decompose up to 800 deg C, but Bunsen goes higher.

Thanks for that link, but sincerely from that diagram it's not so obvious for me to understand that it starts decomposing at 800°C (it even acquires weight some tens of degrees before that point) and that the decomposition is in Na₂O and CO₂.

Google finds also this paper: http://www.tandfonline.com/doi/abs/10.1080/00986440108912851#preview. It can't be read without paying, but google shows quote from the paper:

TGA curve of anhydrous sodium carbonate shows weight loss at the temperature range of 900–1175 K under static air atmosphere [9].

And are you sure that it refers to loss of weight due to decomposition in Na₂O and CO₂ and not, again, to the decomposition in carbonate and water?

 

[Borek]

Thanks for that link, but sincerely from that diagram it's not so obvious for me to understand that it starts decomposing at 800°C

Never stated that, please reread my post - I wrote that it doesn't decompose before 800, it doesn't mean it starts at 800, it means it can be expected to decompose at some higher temp.

that the decomposition is in Na₂O and CO₂.

And are you sure that it refers to loss of weight due to decomposition in Na₂O and CO₂ and not, again, to the decomposition in carbonate and water?

Sorry, no idea what you mean by "decomposition in something". Could be my English fails me.

 

[lightarrow]

Never stated that, please reread my post - I wrote that it doesn't decompose before 800, it doesn't mean it starts at 800, it means it can be expected to decompose at some higher temp.

Ok. So we still don't know for sure at which temperature Na₂CO₃ decomposes according to:

Na₂CO₃ --(heat)-> Na₂O + CO₂

and if it really does it (in absence of other chemicals which reacts with at least one of the products).

Sorry, no idea what you mean by "decomposition in something". Could be my English fails me.

Maybe it's my english, I don't know
I mean that sodium carbonate at room temperature is never pure because it always has some water in it. So when we say it "decomposes" it's not clear which is the reaction, it could simply be

Na₂CO₃*nH₂O --> Na₂CO₃*(n-1)H₂O + H₂O

So, with "decomposes in..." I intended that "it decomposes forming..."

 

[Borek]

Ok. So we still don't know for sure at which temperature Na₂CO₃ decomposes

Right.

and if it really does it

I have no doubts it does. There are no other stable substances it can decompose to, and it has to decompose at some point. Everything does, it is just a matter of temperature.

I mean that sodium carbonate at room temperature is never pure because it always has some water in it. So when we say it "decomposes" it's not clear which is the reaction

No, it is clear. Water leaves crystals at much lower temperatures, before we get to 800 deg C (which we know is still not enough) carbonate is dry as Sahara desert.

 

[lightarrow]

I have no doubts it does. There are no other stable substances it can decompose to, and it has to decompose at some point. Everything does, it is just a matter of temperature.

In that sense, ok. Yes, even water, e.g., decomposes into hydrogen and oxygen at temperatures high enough, but in the case of sodium carbonate how do we know that it doesn't decompose, e.g., in Na and CO₂ and O₂ or Na⁺, CO₃^-- and then in Na, C, O?

No, it is clear. Water leaves crystals at much lower temperatures, before we get to 800 deg C (which we know is still not enough) carbonate is dry as Sahara desert.

Right, even because, otherwise it wouldn't be possible to make standards heating it...