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Born haber cycle help

So i have my chemistry exam in a few hours and i’m confused. When we measure the enthalpy of atomisation of e.g chlorine and it goes cl2>>2cl do we do enthalpy of atomisation times by 2 and with 1/2cl2>Cl what would that be. I’m seeing different things in my notes and in the past paper i’ve done. Also electron affinity of its 2Cl would be 2 x electron affinity right?
no you don't times by 2 when you go from half to 1 for this
you only times 2 when u get the 2 infront of anything :smile: i'd double check with someone else though ! i'm a little confused with this myself
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mxx454
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Original post by bugaboo02
no you don't times by 2 when you go from half to 1 for this
you only times 2 when u get the 2 infront of anything :smile: i'd double check with someone else though ! i'm a little confused with this myself

Thanks i’ll email my teacher hopefully he replies
Original post by mxx454
So i have my chemistry exam in a few hours and i’m confused. When we measure the enthalpy of atomisation of e.g chlorine and it goes cl2>>2cl do we do enthalpy of atomisation times by 2 and with 1/2cl2>Cl what would that be. I’m seeing different things in my notes and in the past paper i’ve done. Also electron affinity of its 2Cl would be 2 x electron affinity right?

This is precisely why you need to learn the enthalpy definitions!

The enthalpy of atomisation is per mole of atoms formed
So, yes, you do need to multiply by 2.

If you are given the bond enthalpy of chlorine, it would be different. 1 mole of bonds makes 2 moles of atoms.
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mxx454
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Original post by charco
This is precisely why you need to learn the enthalpy definitions!

The enthalpy of atomisation is per mole of atoms formed
So, yes, you do need to multiply by 2.

If you are given the bond enthalpy of chlorine, it would be different. 1 mole of bonds makes 2 moles of atoms.

Oh right that makes sense thank you. I’m a little confused with the bond enthalpy though. Like how would they give bond enthalpy in the question, is it the same as Cl2>>2Cl
(edited 2 years ago)
Original post by mxx454
Oh right that makes sense thank you. I’m a little confused with the bond enthalpy though. Like how would they give bond enthalpy in the question, is it the same as Cl2>>2Cl

The bond enthalpy definition is the energy required to break one mol of specified bonds in a gaseous substance.

Cl2(g) ==> 2Cl(g) ΔH = +242 kJ

This is equal to double the enthalpy of atomisation
(edited 2 years ago)
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mxx454
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Original post by charco
The bond enthalpy definition is the energy required to break one mol of specified bonds in a gaseous substance.

Cl2(g) ==> 2Cl(g) ΔH = +242 kJ

This is equal to double the enthalpy of atomisation

Oh thank you sm

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