Lattice Energy Question

[HowAboutDAT]

this is probably a really simple question, I just don't remember it from Gen Chem. Can someone explain it? thanks!

Which one of the following ionic solids would have the largest lattice energy?
a) NaCl
b) NaF
c) CaBr2
d) CsI
d) CaCl2

and

Which of the following solids would have the highest melting point?
a) NaF
b) NaCl
c) NaBr
d) NaI

one more question:
Which one of the following compounds is most likely to be a molecule?
a) KF
b) CaCl2
c) SF4
d) Al2O3
e) CaSO4

so i know ionic compounds are not molecules, so that eliminates a,b and e.

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[Sublimation]

this is probably a really simple question, I just don't remember it from Gen Chem. Can someone explain it? thanks!

Which one of the following ionic solids would have the largest lattice energy?
a) NaCl( now that i think about it Cl has perfect combination of dist. and electro. hmmm ill go with this one scratch B)
b) NaF
c) CaBr2
d) CsI
d) CaCl2

and

Which of the following solids would have the highest melting point?
a) NaF
b) NaCl ( i read the Q incorrectly lol. I would go with this.)
c) NaBr
d) NaI

one more question:
Which one of the following compounds is most likely to be a molecule?
a) KF
b) CaCl2
c) SF4
d) Al2O3
e) CaSO4

so i know ionic compounds are not molecules, so that eliminates a,b and e.

I will take a quick shot at these my gen chem is really rusty. Ait for the first i will go with NaF due to the electronegativity factor that comes into play with F. I would reason taht due to the short distance ( size of molecule and the electonegativity dif.). as for the second i would go with NaI for the size and weak bond i guess. So for the last i kno for a fact Al2O3 is a molecule. SF4 has one lone pair.

 

[sciencegod]

my gen chem is in tip top shape. (sorry I took so long to respond). for first one, answer is cacl2. lattice energu depends on the magnitude of charge and on the size (smaller size higher energy). cacl2 has biggest charge +2 on ca. and cl is smaller and more electronegative.
for second q answer is naf bec f is smallest and most elector.
for third answer is sf4. obviously its a molexule. you guys can debate whether al2o3 is ionic or not. its already been debates and there's no definite answer. anyway, obviously this question asuning its ionic bec metal and nonmetalm. hope that helps.
by the way where these questions from.