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Topic: Boiling point of hydrides  (Read 392 times)

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Offline Studentofhem

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Boiling point of hydrides
« on: August 10, 2019, 07:24:45 AM »
Why are the boiling points of group 16 hydrides higher than that of group 17 hydrides?

Especially H2O and HF I assume that HF would be a stronger Hbonding force than H20. As F is more electronegative. So wouldn’t it therefore have a higher boiling point ?
 
 ???

Thanks for answering have a test on intermolecular forces!

 

Offline chenbeier

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Re: Boiling point of hydrides
« Reply #1 on: August 10, 2019, 08:31:29 AM »
No , what is the boiling point of water and hydrogen fluoride?

Order NH3>PH3<AsH3<SbH3<BiH3

H2O>H2S<H2Se<H2Te<H2Po

HF>HCl<HBr<HI<HAt

And H2O>HF>NH3

The highest values can be seen in the second period. It has to do with the hydrogen bridge bpnding.

Water has the highest value, because Oxygen can coordinate 4 bonds. Ammonia only one so the lowest one. HF can make chains like (HF)2-6

Offline Studentofhem

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Re: Boiling point of hydrides
« Reply #2 on: August 10, 2019, 08:53:21 AM »
Thanks for the answer but I don’t understand if it’s answered my question.

Why does H2O have a higher boiling point than HF?

I understand why NH3 is the lowest. But I thought HF would have a higher boiling point than H20 why’s isnt this the case?

Offline Studentofhem

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Re: Boiling point of hydrides
« Reply #3 on: August 10, 2019, 08:54:08 AM »
No , what is the boiling point of water and hydrogen fluoride?

Order NH3>PH3<AsH3<SbH3<BiH3

H2O>H2S<H2Se<H2Te<H2Po

HF>HCl<HBr<HI<HAt

And H2O>HF>NH3

The highest values can be seen in the second period. It has to do with the hydrogen bridge bpnding.

Water has the highest value, because Oxygen can coordinate 4 bonds. Ammonia only one so the lowest one. HF can make chains like (HF)2-6
Thanks for the answer but I don’t understand if it’s answered my question.

Why does H2O have a higher boiling point than HF?

I understand why NH3 is the lowest. But I thought HF would have a higher boiling point than H20 why’s isnt this the case?

Offline chenbeier

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Re: Boiling point of hydrides
« Reply #4 on: August 10, 2019, 05:07:45 PM »
As I already told, ammonia and hydrogenflouride get only chains. Water get network structures.

Offline Studentofhem

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Re: Boiling point of hydrides
« Reply #5 on: August 10, 2019, 05:38:53 PM »
As I already told, ammonia and hydrogenflouride get only chains. Water get network structures.
is there a general reason why group 16 hydrides have a higher boiling point than 17 hydrides

Offline chenbeier

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Re: Boiling point of hydrides
« Reply #6 on: August 10, 2019, 06:27:55 PM »
It has somethings to do, that the elements in 16 have more metalic charachteristic as the ones in group 17. Halogens all non metallic. Chalcogens after sulfur  to selenium and heavier ones are more like a metal. In 15 arsenium already is a half metal. It has an effect also of the bonding that beside kovalent some ionic part is present.

Offline Studentofhem

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Re: Boiling point of hydrides
« Reply #7 on: August 10, 2019, 06:36:49 PM »
It has somethings to do, that the elements in 16 have more metalic charachteristic as the ones in group 17. Halogens all non metallic. Chalcogens after sulfur  to selenium and heavier ones are more like a metal. In 15 arsenium already is a half metal. It has an effect also of the bonding that beside kovalent some ionic part is present.
thank you

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