# Bond enthalpy/haber cycle help

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#1
1cii

I've drawn it out etc..

I've got

-203 = 289 + (Atomisation of flourine) + 732 - 348 -995

Atomisation of flourine = 79

How is atomisation and bond enthalpy linked?

http://filestore.aqa.org.uk/subjects...5-QP-JUN14.PDF

edit dw got it I think

That atomisation is from 1/2F2 -> F
We want F2 - 2F

(I think)?
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4 years ago
#2
(Original post by Super199)
1cii

I've drawn it out etc..

I've got

-203 = 289 + (Atomisation of flourine) + 732 - 348 -995

Atomisation of flourine = 79

How is atomisation and bond enthalpy linked?

http://filestore.aqa.org.uk/subjects...5-QP-JUN14.PDF

edit dw got it I think

That atomisation is from 1/2F2 -> F
We want F2 - 2F

(I think)?
Yes you got to double it and the electron affinity too
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#3
Yes you got to double it and the electron affinity too
What do you mean sorry?
0
4 years ago
#4
(Original post by Super199)
What do you mean sorry?
they give you from half a mole to one atom and you want one mole to two atoms so you need to double it, also when they give you electron affinity they usually give it per atom so we normally need to double it.
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#5
they give you from half a mole to one atom and you want one mole to two atoms so you need to double it, also when they give you electron affinity they usually give it per atom so we normally need to double it.
Any particular example that comes to mind? Would it be to do with bond enthalpies.
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4 years ago
#6
(Original post by Super199)
Any particular example that comes to mind? Would it be to do with bond enthalpies.
Like this
0
#7
Like this
oh yh.

Ok another question lol; With regards to stability if a reaction is more exothermic is it more or less stable?
I'm on about the formation of Cacl2 in particular
0
4 years ago
#8
(Original post by Super199)
oh yh.

Ok another question lol; With regards to stability if a reaction is more exothermic is it more or less stable?
I'm on about the formation of Cacl2 in particular
What is the specific question because i suspect covalent character may pop up in it.
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#9
What is the specific question because i suspect covalent character may pop up in it.
Nah that to do with theoretical and experimental values.

Have a look at page four if you don't mind https://chemrevise.files.wordpress.c...modynamics.pdf

The most exothermic is the most stable, is that always the case.

Something completely different -> if the most exothermic is the most stable then how come benzene is more stable than the triene (can't remember what its called)? If the triene has a more negative value
0
4 years ago
#10
(Original post by Super199)
Nah that to do with theoretical and experimental values.

Have a look at page four if you don't mind https://chemrevise.files.wordpress.c...modynamics.pdf

The most exothermic is the most stable, is that always the case.

Something completely different -> if the most exothermic is the most stable then how come benzene is more stable than the triene (can't remember what its called)? If the triene has a more negative value
Yeah i know it has to do with exp and theoretical values it is just a popular follow up question to bh cycles, im not sure if you can say it is always the case but when considering enthalpy of formation then yes you can, the wording of the question is unlikely to come up in real exams as it is too vague. Benzene has a delta h value of -252 and 1,4,6 cyclohexatriene has -360 so benzene is more stable ( delocalisation enthalpy), so no i dont think you can generalise like that as it is wrong in benzene`s case.
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#11
Yeah i know it has to do with exp and theoretical values it is just a popular follow up question to bh cycles, im not sure if you can say it is always the case but when considering enthalpy of formation then yes you can, the wording of the question is unlikely to come up in real exams as it is too vague. Benzene has a delta h value of -252 and 1,4,6 cyclohexatriene has -360 so benzene is more stable ( delocalisation enthalpy), so no i dont think you can generalise like that as it is wrong in benzene`s case.
hm ok, thank you very much
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