Solving Nonpolar Solubility: CO2 & CH4

[aclark609]

This is not a homework question. It's the beginning of August for pete's sake.

I read that like dissolves like, but what about the density of the molecules that are being dissolved? For instance in a solution (gaseous or liquid) of CO₂ and CH₄, they are both nonpolar, so they mix. However, CO₂ is quite a bit more dense. So wouldn't it settle to the bottom?

The above situation doesn't make sense to me on why they dissolve in the first place either. I understand how ionic molecules dissolve in a polar substance. For instance, NaCl in H₂O. The crystalline substance, NaCl, is more or less picked apart by water molecules due to attraction of opposite charges, but there is a lack of opposite charge attraction in NON polar molecules other than dispersion forces from what I understand. What makes a nonpolar substance dissolve another one? Is this a situation where "It just does?"

 

[janhaa]

read the link below:

http://www.chemicalforums.com/index.php?topic=37061.0

 

[aclark609]

Glorious. Thanks.

 

[ZacharyM]

The force of gravity is really quite trivial compared to intermolecular forces, even those as weak as induced dipole-induced dipole interactions. So the density of the compounds ends up not really mattering. Another approach to thinking about this is entropy. Things in our universe like to become more chaotic, this is the second law of thermodynamics. So if you put two liquids or gases together they usually mix (unless mixing is too energetically unfavorable, such as in the case of oil and water.)

 

[LudusRex]

I would like to provide some clarification on the solubility of nonpolar substances such as CO2 and CH4. While it is true that "like dissolves like," the density of the molecules does not play a significant role in their solubility.

In the case of CO2 and CH4, their nonpolar nature allows them to mix together because they have similar intermolecular forces. This means that the dispersion forces between CO2 molecules and between CH4 molecules are similar in strength, allowing them to mix and form a solution. The density of the molecules does not affect this process.

Additionally, the solubility of nonpolar substances in other nonpolar substances is not solely dependent on dispersion forces. While these forces do play a role, there are also other factors such as the shape and size of the molecules and their ability to interact with one another. This is why some nonpolar substances may be soluble in one nonpolar solvent but not in another.

Furthermore, the dissolution of nonpolar substances in nonpolar solvents is not a result of "opposite charge attraction" as in the case of ionic compounds in polar solvents. Instead, it is a result of the molecules' ability to interact with each other and form a solution.

In summary, the solubility of nonpolar substances in nonpolar solvents is a complex process that involves multiple factors such as intermolecular forces, molecular shape and size, and molecular interactions. It is not simply a case of "it just does" but rather a result of these various factors working together. I hope this helps to clarify any confusion regarding the solubility of CO2 and CH4.