The solubility of a solute in a solvent (that is, the extent of the mixing of the solute and solvent species) depends on

Options

A. the natural tendency for the solute and solvent species to mix
B. the natural tendency for a system to have the lowest energy possible
C. a balance between (1) and (2)
D. neither (1) and (2)

Answer

3

Explanation

The solubility of one substance in another can be explained in terms of two factors:
One is the natural tendency to mix. This is sometimes referred to as the natural tendency toward disorder. Entropy is a measure of disorder. Thus, the tendency toward disorder can be expressed as a tendency toward increasing entropy. The mixing of substance increases entropy. This increse is one of the primary factors leading to the spontaneous formation of a solution. Consider a vessel which is divided by a removable partition with `O_(2)(g)` on the left and `N_(2)(g)` on the right. When the partition is removed, molecules of the two gases begin to mix. Ultimately, the molecules become throughly mixed through their random motion. We might expect a similar mixing of molecules or ions in other types of solutions.
If the process of dissolving one substance in another involved nothing more than simple mixing, we would expect substances to be completely solube in one another, that is, we would expect substances to be miscible. We know that this is only sometimes the case.
Usually, substance have limited solubility in one another. A factor that can limit solubility is the relative forces of attraction between species (molecules or ions). Suppose there are strong attraction solute species and strong attractions between solvent species, but weak attractions between solute and solvent species. In that case, the strongest attraction are maintained so long as the solute and solvent species do not mix. The lowest energy of the solute-solvent system is obtained then also.
Thus, the solubility of a solute in a solvent depends on a balance between (1) and (2).
As a general rule, "like dissolves like". Oil is miscible in gasoline a sboth are mixtures of hydrocarbons (compoinds of C and H only) while oil does not mix with water because water is a polar substances, whereas hydrocarbons are not.