April 28, 2024, 07:11:14 AM
Forum Rules: Read This Before Posting


« previous next »
Pages: [1]   Go Down

Topic: Born-Haber cycle  (Read 3005 times)

0 Members and 1 Guest are viewing this topic.

Offline KitCh

  • Regular Member
  • ***
  • Posts: 22
  • Mole Snacks: +0/-0
Born-Haber cycle
« on: December 05, 2009, 10:35:09 PM »
Why is the first answer positive and the second answer negative? Aren't they basically the same question?

1 - http://i48.tinypic.com/51ey41.jpg
2 - http://i49.tinypic.com/20aoqpu.jpg


 ???
Logged

Offline UG

  • Full Member
  • ****
  • Posts: 822
  • Mole Snacks: +134/-15
  • Gender: Male
Re: Born-Haber cycle
« Reply #1 on: December 05, 2009, 10:51:53 PM »
I think it's all down to definition really,
Some might define the lattice enthalpy as:
Na+ (g) + Cl- (g)  :rarrow: NaCl (s)  ΔlatH = -786 kJ mol-1
Or:
NaCl(s)  :rarrow: Na+ (g) + Cl-(g)  ΔlatH = 786 kJ mol-1
I think :-\ the latter is 'more correct'
Logged

Offline KitCh

  • Regular Member
  • ***
  • Posts: 22
  • Mole Snacks: +0/-0
Re: Born-Haber cycle
« Reply #2 on: December 05, 2009, 10:55:57 PM »
So Lattice Energy is always positive?
Logged

Offline UG

  • Full Member
  • ****
  • Posts: 822
  • Mole Snacks: +134/-15
  • Gender: Male
Re: Born-Haber cycle
« Reply #3 on: December 05, 2009, 10:58:13 PM »
:D Forget what I said before, I've just checked Wiki and it seems that the former is the one they use:

http://en.wikipedia.org/wiki/Lattice_energy
Logged
Pages: [1]   Go Up
« previous next »
Sponsored Links