My copy (PDF) of Levine's Physical Chemistry (6th ed.), page 570-571, section: "Adsorption of Gases on Solids", states:

Physical adsorption is nonspecific. For example, $\ce{N2}$ will be physically adsorbed on any solid provided the temperature is low enough.


... N2 is chemisorbed at room temperature on $\ce{Fe, W, Ca,}$ and $\ce{Ti}$ but not on $\ce{Ni, Ag, Cu,}$ or $\ce{Pb}$.

Alright, fair enough, thanks for the examples.


A bunch of (notoriously error-prone-citation-deficient) course books issued by my school, all unambiguously concur on the contrary:

At $\ce{83K}$, $\ce{N2}$ is physically adsorbed over iron metal. Raising the temperature to $\ce{773K}$ then results in the nitrogen being chemisorbed over the metal as atomic nitrogen.

Which in other words is: "At room temperature, nitrogen is physically adsorbed. The nitrogen is chemisorbed after the temperature's raised to 500 degrees Celsius".

But this contradicts the information in Levine's book.

Who's right here: Levine or my book? (References are welcome) O:)


LinearChristmas has correctly pointed out that the temperatures at which the physical adsorption --> chemisorption transition takes place depends on pressure as well as the nature of the iron surface.

In light of this, I'll modify my question:

Q- My coursebook and Levine's lists (implicitly in Levine's case) the transition from physical adsorption --> chemisorption at different temperatures. Between the two, which one lists the more improbable temperatures?


closed as too broad by getafix, Mithoron, Geoff Hutchison, Todd Minehardt, airhuff Jan 1 '18 at 20:13

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Unfortunately, I don't think this can be answered as is. This probably isn't entirely your fault; general textbooks tend to be secretive when it comes to experimental details. Firstly, what are the pressures and how were measurements done on each? It is also incorrect to assume an iron as being equivalent to some other iron. Surface properties, including porosity, are strongly dependent on how the material has been handled. I further recommend adding references for both sources. Finally, is it also possible $773\ \mathrm{K}$ was simply a typo for $273\ \mathrm{K}$? (just in case) $\endgroup$ – Linear Christmas Dec 1 '17 at 17:31
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    $\begingroup$ @Linear A good point! Not sure about the iron surface/crystal, but I just assumed this is carried out at atmospheric pressure (unlikely, but I wouldn't know any better). As for the 773/273 typo, it could be a typo, but three different booklets (all issued by our teacher) carry 773 in it. :'( $\endgroup$ – paracetamol Dec 1 '17 at 17:35
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    $\begingroup$ Okay. Sadly, we still have to know more about the iron to make an informed comparison. For example, 10.1039/TF9595502166 reports on some iron catalysts having chemisorbed N2 at measurable rates from $473\ \mathrm{K}$. Their own sample, ‘highly reduced singly promoted iron catalyst’, reported similar results for a temperature of $273\ \mathrm{K}$. There is another caveat. The second source in OP: chemisorbed over the metal as atomic nitrogen. Note that there are other ways of nitrogen chemisorbing, though mononitrogen could be most common (I'm unsure). $\endgroup$ – Linear Christmas Dec 1 '17 at 18:17
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    $\begingroup$ @Linear < Nods sadly > This seems more painful than I first thought. I suppose then, any potential answer would be aiming to dismiss either one of the two claims (in my post) as "improbable" rather than outright "incorrect". Thanks for the insight! O:) $\endgroup$ – paracetamol Dec 1 '17 at 18:29
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    $\begingroup$ Yes, I'm afraid so. I do see a scenario where this is closed as primarily opinion-based. To be sure, we may wait for other responses since this is a relatively new thread. $\endgroup$ – Linear Christmas Dec 1 '17 at 18:37

I think you are misinterpreting the course book issued by your school since it never mentions what happens at room temperature.

For me, none of the books is (seems) wrong, because they do not contradict each other. I will mention each affirmation including the textbook which said it (Levine, or Your book):

  • Levine says: N2 is physically adsorbed on any solid at low temperature. This agrees with your text saying N2 is physically adsorbed at 83 K on Fe.
  • Levine says: N2 is chemisorbed at room temperature on Fe. Your book does not mention about room temperature. No contradiction here.
  • Your book says N2 is chemisorbed at 773 K. Levine does not mention this temperature, but if it already occurred at room temperature it will also occur at higher.

The only 'gray area' is at which temperature does N2 get chemisorbed (room temperature or not?). In the article of deBoer et al. mentioned by @Linear Christmas above, they measure chemisorption of N2 even at 23.9 ºC.

They clearly state:

Hitherto it has been reported in literature1,2that an iron catalyst starts to chemisorb nitrogen at a measurable rate at about 200°C. The chemisorption activity of our intensely reduced sample was considerably higher ; already at 0ºC, nitrogen was chemisorbed at a measurable rate.

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    $\begingroup$ "Raising the temperature to 773K then results in the nitrogen being chemisorbed..." <--- That sounds like my book says that at 773K and above nitrogen is chemisorbed, meaning at lower temperatures (including room temp) it is physically adsorbed... so I'm not very confident about your 2nd and 3rd bullet point. First bullet is okay. $\endgroup$ – paracetamol Dec 2 '17 at 7:39
  • $\begingroup$ Being chemisorbed above 773 K does not exclude being also chemisorbed below. $\endgroup$ – Nando Dec 2 '17 at 8:43

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