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Rank these compounds by their expected boiling point.CH3Cl, CH4, CH3OH

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zorico91 | (Level 2) Honors

Posted September 11, 2012 at 9:11 PM via web

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Rank these compounds by their expected boiling point.

CH3Cl, CH4, CH3OH

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted September 12, 2012 at 8:02 AM (Answer #1)

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In these compounds moles are attached to each other by intermolecular bonds. We need to break these bonds in order to allow the substance to evaporate or reach boiling point. So if the strength of such bond is high then we need lot of energy to break them and reach the boiling point. On the other hand if the bond is weak we need less energy.

 

`CH_3Cl`

`CH_3Cl ` has dipole-dipole interactions because H is positively charged and Cl is negatively charged. So in `CH_3Cl ` between these positive and negative charges there will be a bond between `CH_3Cl ` moles. These bonds have moderate strength.

 

`CH_4`

In `CH_4 ` there is no powerful bonding. Small opposite charges between `CH_4` atoms will keep them together.These are called Vander vall forces.

 

`CH_3OH`

In `CH_3OH` we have hydrogen bonding because H can bond with a long pair of oxygen. These bonds are very powerful.

 

So Hydrogen bonding is the most powerful. We need more energy to reach boiling point.

Dipole attractions are low in strength than H bonds. So they will have to give less energy than H bonding compound to reach the boiling point. vandervall bonds need less energy to reach boiling point.

 

So;

`CH_3OH` has the highest boiling point.

`CH_3Cl` has a boiling point less than `CH_3OH`

`CH_4 ` has the lowest boiling point.

 

Boiling point

`CH_3OH > CH_3Cl > CH_4`

 

Sources:

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