<p>65% as previously mentioned in this thread
it's easy trust me</p>
<p>a, c and e are metal oxides, therefore ionic, therefore high mp
d is network covalent therefore high mp
b is covalent, therefore low mp (most covalents are gases or liquids at RT)</p>
<p>its the lightest molecule so its london dispersion forces are the weakest...LDF are used to condense gases to liquids...so since they are the weakest in NO2 it would be a gas</p>
<p>none of the other compounds have LDF's.</p>
<p>thanks a lot</p>
<p>Oh, wow. a 65%?!?! HAHA. That's not bad at all. I used to think you needed 3/4 of it right. Guess not...</p>
<p>Every atom/molecule has LDF to some extent.</p>
<p>i thought all molecules had LDFs?</p>
<p>how about an organic frq!!!=[[[[[[[[[</p>
<p>wait....ion dipole interaction is not LDF, at least i think....</p>
<p>all molecules have LDF's, not all compounds.</p>
<p>Ex NaCl is an ionic lattice - no LDF's that matter</p>
<p>Im confused then. Can you explaint he difference between molecules and compounds? And why doesnt NaCl have LDF's?</p>
<p>could somebody please explain Chromatography to me?</p>
<p>Can someone explain the absorbance question for 2004 FRQ? It says that In(X/Xo) = kt, why is it not In(Xo/X) = kt like reaction rates? Where Xo = initial concentration. Why would k be calculated differently here?</p>
<p>
[quote]
Im confused then. Can you explaint he difference between molecules and compounds? And why doesnt NaCl have LDF's?
[/quote]
</p>
<p>NaCl has an ionic bond</p>
<p>LDF are only between nonpolar molecules</p>
<p>Okay, thanks.</p>
<p>Ionic compounds are very unique. The electronegativity difference is so great, that one element completely takes an electron from another, and 2 ions form. These ions have a strong attraction, and stick to each other, and are very hard to separate. There are no LDFs because there is no shifting of electrons. You cant have 2 NaCl molecules come close to each other, because there is no such thing as an NaCl molecule. They form tight lattices with each Cl surrounded by Na and every Na surrounded by Cl.</p>
<p>No, I definitely just read 2 seconds ago that LDF are for ALL bonds, regardless of whether they are polar or nonpolar.</p>
<p>When comparing physical properties like MP, BP, dHvap, dHfus, etc you need to compare forces between particles. There are 4 categories:
1) network covalent - one giant molecule with atoms joined by covalent bonds
2) ionic compounds - atoms with large electronegativity differences joined together (metals joined to nonmetals like NaCl)
3) metals - all the metals listed on the periodic chart, Cu, Fe, Na, etc
4) covalent compounds - atoms with small electronegativity differences joined together (usually all nonmetals like CO2, N2O, Cl2, H2O</p>
<p>Additional vocab
Smallest piece of an element is an atom
Smallest piece of a covalent compound is a molecule
Smallest piece of an ionic compound is a formula unit
It's not correct to call an ionic compound a molecule</p>
<p>LDF's are in all covalent compounds, whether they are polar or nonpolar. NaCl isn't polar, its ionic</p>