EK chemistry #763

[yingao88]

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which of the following molecular hydrides has the highest boiling point?
A. SiH4
B. H2Te
C. H2S
D. SnH4

the explaination in the back of the book mention the molecular weight, however i was thinking of the polarity of the molecule, the dipole-dipole interaction. So when hydrogen bond is not a concern, molecule weight prioritize?

 

[BestDoctorEver]

which of the following molecular hydrides has the highest boiling point?
A. SiH4
B. H2Te
C. H2S
D. SnH4

the explaination in the back of the book mention the molecular weight, however i was thinking of the polarity of the molecule, the dipole-dipole interaction. So when hydrogen bond is not a concern, molecule weight prioritize?

I would think molecular weight takes precedent over dipole in that case if the difference is big.

 

[Postictal Raiden]

which of the following molecular hydrides has the highest boiling point?
A. SiH4
B. H2Te
C. H2S
D. SnH4

the explaination in the back of the book mention the molecular weight, however i was thinking of the polarity of the molecule, the dipole-dipole interaction. So when hydrogen bond is not a concern, molecule weight prioritize?

is the answer B?

 

[Jepstein30]

I would think molecular weight takes precedent over dipole in that case if the difference is big.

Yep!

Looked it up in my book and the answer is B. It does say that "because none of these can h-bond, you should look at MW".. did learn in Orgo though that MW is 1st thing to look at and should be considered if the difference is large so I would probably have picked the heaviest molecule even if one other could h-bond but that'd be wrong based on a quick wikipedia search.

H-bond > MW > dipole > vdw

I guess.. which doesn't really make a ton of sense considering H-bond is just a really strong dipole-dipole.

 

[Postictal Raiden]

Yep!

Looked it up in my book and the answer is B. It does say that "because none of these can h-bond, you should look at MW".. did learn in Orgo though that MW is 1st thing to look at and should be considered if the difference is large so I would probably have picked the heaviest molecule even if one other could h-bond but that'd be wrong based on a quick wikipedia search.

H-bond > MW > dipole > vdw

I guess.. which doesn't really make a ton of sense considering H-bond is just a really strong dipole-dipole.

I'm confused with the statement that none of given compounds is capable of H-bonding. I thought since all of them possessed Hydrogen, then they all must be able to participate in H-bonding. Or do we only consider the central atom when we decide whether a molecule is capable of h-bonding?

 

[Bru]

The hydrogen needs to be attached to a Highly electronegative element (F, O, N) in order to engage in hydrogen bonding.

 

[Temperature101]

The hydrogen needs to be attached to a Highly electronegative element (F, O, N) in order to engage in hydrogen bonding.

Yep.... If H is not attached to one of these elements, there is no H bond. Period.

 

[slz1900]

I have read that hydrogen bonded to a sulfur atom is able to form very weak hydrogen bonds and wikipedia says so as well.