## elisichi 2 years ago I am studying the Haber process, and it says that to obtain nitrogen, hydrogen is burned in the air, so that it combines with oxygen and leaves nitrogen. Could anybody help me elaborate a balanced equation for this statement?

1. EmmaH

wow this is out of my league i am only ok at bio ....really sorry

2. elisichi

Its okay :) Dont worry about it!

3. stewie

4. elisichi

no :(

5. stewie

alright ill try and find the answer

6. stewie

do you have notes on this i can look at

7. elisichi

no, nothing really... because its an essay we are supossed to write

8. Carl_Pham

$2 {\rm H}_2(g) + {\rm O}_2(g) \rightarrow 2 {\rm H}_2{\rm O}$ However, if it matters, I believe this statement is wrong, if you are talking about current industrial processes. Hydrogen is fairly expensive to produce, and the normal way in which nitrogen is extracted from air industrially is to cool the air. The other major components will all condense (to liquid or solid) before nitrogen -- water will freeze at 0C, CO2 will condense at 195K, oxygen will liquify at 90K, argon will liquify at 84K. Nitrogen itself does not liquify until 77K. Of course, in the laboratory setting it might be easier to proceed by burning H2. Or maybe you are referring to historical processes.

9. Carl_Pham

Sorry I left out the final (g) on the H2O in the chemical equation. You'd also have to do cool the reaction mixture after the combustion if you wanted to remove the water vapor.

10. elisichi

Yes I have seen that equation, but I wanted to include nitrogen somewhat because its part of the air, so that it is shown in the equation.. but i dont know how to do that

11. elisichi

like I don't want the ionic equation, but the 'whole thing' if you know what I mean :D

12. Carl_Pham

The nitrogen isn't reacting, so it isn't part of the equation. You can certainly add it to both sides if you like:${\rm N_2}(g) + 2 {\rm H}_2(g) + {\rm O}_2(g) \rightarrow 2 {\rm H}_2{\rm O}(g) + {\rm N}_2(g)$ But that really doesn't tell you anything interesting.

13. elisichi

Hmm, so you think it's better if I write the first one and then explain that nitrogen is included as well rather than writing the second one?

14. Carl_Pham

What are you trying to say? What's the point you're trying to make? If what you're sayiing is that burning H2 in air will remove the oxygen, the first equation is sufficient. You should also say something about the stoichiometry, pointing out that the equation tells you that you need 2 volumes of H2 for every volume of O2 you want to remove, e.g. to remove 1L of O2 you'd need to burn 2L of H2. To be 100% sure you get all the O2, you'd probably want to include an excess of H2, in fact.

15. Carl_Pham

I'm also curious: you say "it says" that H2 is burned to remove O2 from air. Can you tell me what "it" is? That is, what source is making this statement? A textbook? Online source? Article? I'd be very interested in knowing the specific source.

16. elisichi

Never mind, never mind. I get it. My mind was just doing something weird to me. hahah! Of course I dont need the nitrogen, cause it's pointless since it's not showing anything. Thank you soo much :D

17. Carl_Pham

So can you tell me what source says N2 is produced by burning H2 in air?

18. elisichi

It's a website. We are to write an essay and I've been researching

19. elisichi

Why?

20. Carl_Pham

I ask because I believe that statement is likely to be in error, and it's important to know what sources might be spreading error. The profession of chemistry instruction needs to police itself.

21. elisichi

I don't believe it's an error. In fact, it makes sense. For the Haber process, you need nitrogen and hydrogen. The air is made of mostly nitrogen and oxygen. By burning hydrogen in the air, hydrogen and oxygen combine together. And it is, therefore, easier to extract nitrogen, so it can be later on used for this process. I didn't mean the reaction produced nitrogen literally. I didn't express myself correctly there. So blame me not the source.

22. Carl_Pham

No, sorry, that's not correct. Or rather, you certainly COULD do it that way, but that's not in fact how it's actually done. As I said above, nitrogen is extracted from air by what's called fractional liquefaction -- you cool the air until everything except the nitrogen condenses. A very good canonical print reference for industrial processes is "Survey of Industrial Chemistry" by Philip J. Chenier. Has every chemical you could want, with details of how it's produced and used. Your library will have a copy.

23. elisichi

Are you a 100% sure? Because, it's from the BBC... http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/chemreac/energychangesrev3.shtml

24. Carl_Pham

Yes, I'm sure. I'm looking at the site now. You're right that it would be a little surprising to find the BBC writing nonsense, but it could happen. Let me have a look. Thank you very much for supplying the link. Let me see if I can find you a good authoritative source. I'll also look over that BBC site to be sure they haven't said anything else that's weird.

25. elisichi

Exactly, I doubt the BBC would write incorrect stuff, especially considering that it's Bitesize, a site that thousands of students use as a learning resource.

26. Carl_Pham

Sure, but it could happen. The problem here is that this is contradicted by even more authoratative sources -- for example, the one I gave you, which is a standard textbook in industrial chemistry written by a chemical engineering professor at the University of Wisconsin, and used all over the country to teach chemical engineers. Which is more likely, do you think? That a standard chemical engineering textbook is wrong (and has been for decades), or that whoever wrote the BBC website made a booboo?

27. elisichi

Are you sure that book is on the Haber process? and not some other process? Of course, I agree it's possible. The internet is full of unreliable bullpellet these days.

28. Carl_Pham

Tell you what: google "Haber process" or "industrial production of ammonia" and see if you can find a single other source that suggests the nitrogen comes from burning H2 in air. So far the BBC is the only one I can find. I'm still looking...

29. elisichi

I was actually doing the exact same thing right now. Great minds think alike.

30. elisichi

I found another source that agrees with the BBC. http://www.warwickshire-ecosiht.org.uk/subject/science/Haber_process_000.htm

31. elisichi

Yet, I cannot guarantee it's very reliable...

32. elisichi

Anyway, you deserve a medal.

33. Carl_Pham

It's exactly the same image. These sources clearly copied from each other, but which came first is unclear.

34. Carl_Pham

OK, I think it might be right at least in Europe, at least some of the time. Here's an extremely authoritative source: http://www.ocinitrogen.com/Media%20Library/Ammonia%20process%20-%20BAT%20Production%20of%20ammonia%20(2000)%20-%20Brochure.pdf That is a brochure produced by the European Fertilizer Manufacturer's Association, and made available on the website of a European company (OCINitrogen) that actually manufacturers ammonia industrially. So there's no doubt about that. The brochure is fairly technical, but they describe two processes for making ammonia. One proceeds basically according to the same diagram on the BBC site, in which as part of the steam reforming part of making H2 from methane, some of the H2 produced is burned and removes the O2 from the air, which is then passed straight on to the ammonia synthesis stage. There is another process that uses N2, presumably supplied by liquefaction of air. So at least in Europe, at least for one major process, the BBC site is right and I and the standard reference textbook is wrong. Amazing! This has been very educational. It may be that the process generally used in the United States differs, of course. There are distinctions based on what resources are convenient, and those vary from country to country.

35. elisichi

Ok, that makes sense! I can write about that on my essay! Thank you so much for taking your time. You don't know how much I truly appreciate it. I'd give you 1000 medals if I could.

36. Carl_Pham

The pleasure is mine. This has been a fascinating exercise. I found a few more references that suggest that some plants use the burning of some of the H2 to make the N2, and others use N2 from liquefaction of air. I can't find out which is more often used, nor what determines which is preferred. Good luck.