Why does CHBr3 and C10H22 have higher boiling points than water?

[匿名]

2016-02-21 4:13 am

I am a bit confused because CHBr3 is polar and should have dipole-dipole forces in it, which are said to be weaker compared to Hydrogen bonds. Also, C10H22 (Decane) should have London forces, which are also much weaker compared to the Hydrogen bonds in water. So then why do CHBr3 and C10H22 have respective boiling points of 150 degress celsius and 174 degrees celsius?

回答 (2)

andrew

2016-02-21 4:47 am

✔ 最佳答案

Note that "dipole-dipole forces are weak than hydrogen bonds" is only held on comparing small molecules with comparable sizes. However, the sizes of CHBr₃ and C₁₀H₂₂ are much greater than that of water.

The greater the molecular size, the strong the van der Waals' forces between molecules are. The sizes of CHBr₃ and C₁₀H₂₂ are great enough to have van der Waals' forces between molecules greater than the hydrogen bonds between water molecules. Therefore, the boiling points of CHBr₃ and C₁₀H₂₂ are higher than that of water.

Besides, the size of C₁₀H₂₂ is much greater than CHBr₃. Therefore, the van der Waals' forces between C₁₀H₂₂ molecules are stronger than those between CHBr₃ molecules, and thus the boiling point of C₁₀H₂₂ is higher than that of CHBr₃.

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[匿名]

2016-02-21 4:33 am

Take a look at their molecular weights!

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