boiling pt: Solely colligative?

[sv3]

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Came across a question today that asked wether HF in solution or HBr in solution had the higher boiling point.

I thought HF due to H bonding but the answer was HBr b/c HF wouldn't fully dissociate and BP is a colligative property - thus more particles are present in HBr solution than HF, and HBr has the higher boiling point.

So why am i not supposed to consider H bonding here? I just don't understand how it can be neglected as it was so key throughout orgo and lots of gen chem. any help would be great

thanks
steve

 

[RogueUnicorn]

h-bond would be considered if you're comparing PURE HF to PURE HBr. you're not, you're dealing with solutions and therefore the colligative properties of WATER and the boiling point elevation thereof.

 

[wanderer]

Does boiling point elevation have to do with the forming of stronger bonds (such as ion-dipole)?

If that were the case the extra ion-dipole bonds between Br - and water would be more significant than the weaker H-bonds formed between HF and water....

 

[RogueUnicorn]

no it doesn't, it occurs because essentially you're diluting out the solvent as you dissolve solute into it.

 

[sv3]

duh