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N to N2


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3 hours ago, observer1 said:

At what temperature and pressure should i keep a cylinder filled with N (NOT N2) so that they do not react and form N2

Absolute zero and less than 1 mTorr.😁

Seriously,, forget it. There is almost no activation energy for this recombination. So you can only slow it down by lowering the rate of interatomic collisions.

Edited by exchemist
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is that the max temperature and pressure? cuz u cant reach it so like is there a catalyst that stops the reaction or increases the temperature required for N to become N2?

13 minutes ago, exchemist said:

Seriously,, forget it. There is almost no activation energy for this recombination. So you can only slow it down by lowering the rate of interatomic collisions.

BRUH

how can i calculate collisions of an atom if i know the temperature, pressure and volume

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7 minutes ago, observer1 said:

is that the max temperature and pressure? cuz u cant reach it so like is there a catalyst that stops the reaction or increases the temperature required for N to become N2?

BRUH

how can i calculate collisions of an atom if i know the temperature, pressure and volume

Catalysts reduce activation energy, not increase it. Collision rate - that’s a kinetic theory question. You would also need to know the effective diameter of the atoms, but I’m sure that’s available. I’d need to think how to do that when I get out of bed and have moment later in the day. Someone else may offer an answer in the meantime.

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I would say N alone is not existing. If for some reason it is present it will react directly to N2 or react with other atoms.

It was reported you find it during thunderstorm in lightnings.

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This is a different thing. First also hydrogen is present and for making ammonia catalysts are used. So there are surface reactions . Has nothing to do with breaking up a nitrogen molecule and keep it atomic.

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The heat of dissociation of diatomic molecular nitrogen is given as 226 kcal/mole along with the statement in Latimer and Hildebrand

Quote

It may be calculated from thermal data that at 8,000oC the gas is only about 40% dissociated into elemental nitrogen.
Under the influence of a high voltage discharge the nitrogen molecule is 'activated'. Active nitrogen appears to be atomic nitrogen in which one or more electrons are raised  to higher energy levels. Active nitrogen continues to glow for some time after discharge has been stopped.

 

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9 hours ago, observer1 said:

is that the max temperature and pressure? cuz u cant reach it so like is there a catalyst that stops the reaction or increases the temperature required for N to become N2?

BRUH

how can i calculate collisions of an atom if i know the temperature, pressure and volume

OK, I've looked this up and to be honest it is a bit confusing, between the collision rate for an individual molecule, total collisions for a given absolute number of molecules and a total collisions per unit volume. Also, a lot of the formulae are for reactions between 2 different species, so they are for molecules of type A colliding with molecules of type B, etc.  

But as far as I can see, and simplifying the formula as far as possible, it looks to me as if, for a gas consisting of a single type of molecule, the total number of collisions expected in unit time per unit volume is: 

Z = 2N²d²√(πkT/m), where:

Z is the no. of collisions per unit volume per unit time

N is the no of molecules per unit volume (i.e. number density)

d is the effective diameter of the atom or molecule for interacting in a collision (atoms and molecules are not hard spheres of course)

k is Boltzmann's constant

m is the mass of the atom or molecule

T is absolute temperature

(The derivation of this formula is extremely hairy, by the way, as it has to allow for the fact that all the atoms of molecules are moving in random directions.)

You can use 2 x atomic radius for d, which will be good enough for an approximate answer (order of magnitude).

You can see the number of collisions goes up with the square of the number density, and with the square of the atomic or molecular diameter, and with the square root of temperature.

Number density is fairly easily obtained from the ideal gas equation PV=nRT.  I mole of any (ideal) gas occupies 22.4l at STP, viz. 273.15K (0C) and 1bar pressure. 

But I don't know what you are going to do with this information. You won't stop N atoms recombining at any practical temperature or pressure. 

In fact, if your idea is to use separated nitrogen atoms as an energy store, that can release energy when N2 is re-formed, I think you are better off to segregate the N atoms in molecules that when suitably brought together generate N2. For instance, ammonia is now talked about as a future fuel for ships. More about ammonia combustion here:

https://www.sciencedirect.com/science/article/pii/S1540748918306345

Edited by exchemist
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i searched more and now.............
what if i broke the N2 bond by keeping it in 500+ degree C and 200 atmospheres(without hydrogen). this is how nitrogen is split and reacts with hydrogen to form ammonia. if i keep the broken N atoms in the thing, they would not combine that much since if the join they release energy and the temperature increases, causing the bond to break agian.

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7 hours ago, observer1 said:

i searched more and now.............
what if i broke the N2 bond by keeping it in 500+ degree C and 200 atmospheres(without hydrogen). this is how nitrogen is split and reacts with hydrogen to form ammonia. if i keep the broken N atoms in the thing, they would not combine that much since if the join they release energy and the temperature increases, causing the bond to break agian.

You could, but using a highly compressed gas at over 500C might not be the most convenient or efficient form of energy storage. 

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On 8/21/2022 at 4:47 PM, observer1 said:

but it does give the most energy per mole compared to the normal oxygen and hydrogen mixed to form water

Where do you get 500C from, though?

If we look at the equilibrium N2(g) <-> 2N(g), this will be in balance, with similar amounts of N and N2, when  ΔG = 0. Since  ΔG=ΔH-TΔS, that will happen when TΔS= ΔH, which will be at the temperature at which where T= ΔH/ΔS.

ΔH =945kJ/mol, but according to what I have been able to dig up, ΔS seems to be around~100J/K-mol. That would imply an absolute temperature of 945 x 1000/100, 9450K, which is over 9,000C, well above the boiling point, repeat boiling point, of iron! 

 

 

Edited by exchemist
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ok so industries used osmium (now nickel) to reduce the pressure and temperature needed to break the triple bond and kept it with H2. The osmium Reduced the energy needed to 500C and 200 Atmospheres. in that situation the nitrogen broke and reacted with the hydrogen to form ammonia. 

7 minutes ago, chenbeier said:

I think this is only possible on or in the Sun.

also lightning

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1 hour ago, observer1 said:

ok so industries used osmium (now nickel) to reduce the pressure and temperature needed to break the triple bond and kept it with H2. The osmium Reduced the energy needed to 500C and 200 Atmospheres. in that situation the nitrogen broke and reacted with the hydrogen to form ammonia. 

also lightning

Not really. The way you describe it misrepresents the mechanism of this reaction. This is the Haber process. The N2 molecule is adsorbed on the surface of the catalyst, where it forms a kind of nitride with it, first end-on and then sideways-on, which then reacts, still on the surface, with adsorbed H to form an adsorbed NH, NH2 and finally NH3, before desorption of ammonia occurs. At no stage are free N atoms produced.

This is not a route to formation of atomic nitrogen. 

 

Edited by exchemist
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5 minutes ago, chenbeier said:

Already mentioned before

Quite right, so you did. I've just filled in a few more details for our poster, to help him or her understand why it is not what he or she thinks.  🙂

Edited by exchemist
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13 minutes ago, chenbeier said:

I think there will be no more new information so the topic can be closed by admin.

Well, let's first of all see if our poster is now satisfied with the answers we have given, or if he or she wants to go somewhere else with the topic. It is, after all, a chance to discuss some chemistry. 

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