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LoginClarify this lattice energy proportional to..
3 posts
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is L.E proportional to
1.(charge of cation X charge of anion) / interionic distance between ions or
2.(Charge of cation X Charge of anion)/ THE SQUARE of (interionic distance between ions)
the calculation for L.E is the same for the calculation of force of attraction between ionic bonds?
my school notes suuuccckkk badddd,hopefully any forumers have any notes to spare can pm me for a deal..
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Moderator'A' & 'O' Levels Chemistry & Biology Ex-MOE Teacher Tutor
840 posts since May '05-
This is indeed a most intriguing question, with an equally fascinating answer!
Lattice energy is determined by Coloumb's Law :
http://en.wikipedia.org/wiki/Coulomb's_law
The magnitude of the electrostatic force between two point electric charges is directly proportional to the product of the magnitudes of each charge and inversely proportional to the square of the distance between the charges.
In other words, F = k [ (Q on cation x Q on anion)/ r^2 ]
So on first glance, you might think that option 2 is correct.
HOWEVER, because energy = force x distance (r), multiplying both sides of the equation by r, you get :
r x F = r x k [ (Q on cation x Q on anion) / r^2 ]
r x F = k [ (Q on cation x Q on anion) / r ]
E = k (Q on cation x Q on anion) / r
Therefore, option 1 is correct.
Edited by UltimaOnline 22 Jun `08, 11:47PM
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