Comparing Melting Points

[sudo]

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What's the order of reasoning for you guys when you have to compare melting points of various compounds? My reasoning might be in the wrong order, but here's what I do:

1. Compare molecular weights
2. If molecular weights are approximately equal, look at intermolecular forces.
3. Ion-Ion=higher MP; ion-dipole=medium MP; dipole-dipole (H-bonding)=lower MP

Is my reasoning (and order of reasoning) correct??

Thanks

 

[FutureDoc2]

What's the order of reasoning for you guys when you have to compare melting points of various compounds? My reasoning might be in the wrong order, but here's what I do:

1. Compare molecular weights
2. If molecular weights are approximately equal, look at intermolecular forces.
3. Ion-Ion=higher MP; ion-dipole=medium MP; dipole-dipole (H-bonding)=lower MP

Is my reasoning (and order of reasoning) correct??

Thanks

I was always under the impression that you look at Intermolecular forces first before considering MW. But when comparing size, the bigger molecule will have greater Intermolecular Forces. Higher Intermolecular Forces lead to higher BP and higher MP.
So..

Higher BP >>>>>>>>>Lower BP
Ionic/Network Covalent>>Hydrogen Bonds>>Dipole-dipole>>London Dispersion Forces.

Hope this helps!