Boiling point

Small potato

2015-06-12 3:43 am

boiling pt of oxygen=−183 °C
boiling pt of argon=−186 °C

1.The relative atomic mass of oxygen gas is 32 while the relative atomic mass of Ar gas is 40. They are both non polar molecule.
So there is only dispersion force between O2 molecule and Ar atom
The strength of dispersion force increase with molecular mass
So the dispersion force of Ar should be stronger than that of O2
So the boiling point of Ar should be higher than that of oxygen

But why the boiling point of Ar is lower than O2 as shown ?

回答 (1)

用戶26240

2015-06-12 7:49 am

✔ 最佳答案

Theboiling point of a molecular compound depends on several factors : such asmolecular size, diffusion of electron cloud, molecular mass.

Ar has a higher molecular mass than O2, and this factor makes Arhave a higher boiling point than O2. However, O2 moleculeis diatomic while Ar is monatomic. Therefore, O2 has a largermolecular size and more diffused electron cloud. These two factors make O2have a higher boiling point than O2.

When all the factors are considered, O2 and Ar have comparativeboiling point, and it is found O2 has a slightly higher boilingpoint than Ar.

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