Chemical Forums

Chemistry Forums for Students => High School Chemistry Forum => Topic started by: bubaKazouba on January 02, 2013, 07:11:56 PM

Title: comparing lattice energies (not calculation)
Post by: bubaKazouba on January 02, 2013, 07:11:56 PM

this is the question:
http://i.img-share.net/sTGgfY1TB4.png

13a)
I think the answer should be C because CaO has the highest difference between the anion and cation in the ionic radii, so the anion will be more polarised, so more covalent characters so more lattice energy
but my teacher says its D I'm really confused I don't know.
---------------------
13b) I don't konw what to do about B Li2O because there are 2 Li
Please help thanks in advance :)

Title: Re: comparing lattice energies (not calculation)
Post by: Borek on January 03, 2013, 03:52:22 AM

a. This is most likely purely about electrostatic interactions (so treat them all as purely ionic).

b. And this one is most likely about the least ionic character.

I don't like the question. They want you to use contradicting approaches to answer a and b.

Title: Re: comparing lattice energies (not calculation)
Post by: bubaKazouba on January 03, 2013, 04:23:29 PM

thank you for your reply  :), but sorry I don't understand
what will I do if I treat them as completely ionic?

Title: Re: comparing lattice energies (not calculation)
Post by: Borek on January 03, 2013, 04:25:54 PM

Lattice energy will be just a function of charges and distances (coulomb forces).

Title: Re: comparing lattice energies (not calculation)
Post by: bubaKazouba on January 03, 2013, 05:06:07 PM

Oh yeah I get it Thank you very much
but I still dont get b)

Title: Re: comparing lattice energies (not calculation)
Post by: souro10 on January 10, 2013, 03:44:36 PM

You have already got the answer to question (a).

For (b) , you need to find out the compound which has most covalent character. Why is Calcium Sulfide almost insoluble in water?