We can make only qualitative predictions about the solubility of one substance in another. The best rule for predictions is that like dissolves like, meaning that

Options

A. a solute will dissolve in any solvent that is chemically similar
B. a solute tends to dissolve in solvents that are chemically similar to it
C. a solute will dissolve in any solvent is phusically as well as chemically similar
D. a solute tends to dissolve in solvents that are physically as well as chemically similar to it

Answer

2

Explanation

The most important characteristics in determining similarity are polarity and chemical properties. The formation of hydrogen bonds also has an important effect on solubility.
Many ionic compounds are extremely insoluble in polar solvents, even water. Many nonpolar substances are externally insoluble in nonpolar solvents such as octane. The like-dissolves-like rule tells us only relative solubilities. For example, salt that has law solubility in water generally will be even less solube in nonpolar solvents.
Soaps and detergents provide an interesting application of the like-dissolves-like rule.
A molecule of soap or detergent consists of a long nonpolar hydrocarbon chain with an ionic or hydrogen-bonding group at one end. The nonpolar portion of the molecule tends to dissolve in nonpolar substances such as grease. The polar end of the molecule tends to dissolve in polar solvents, such as water.
In a system containing both water and grease, the hydrocarbon portion of the molecule becomes associated with the grease while the polar group is associated with the water molecules. The soap or detergent molecule is carried away with the water carrying grease and other nonpolar dirt with it.
The rule that like-dissolves-like also helps explain the orientation of large organic molecules in aqueous media for example, of proteins in a living cell or of fats in the membrane surrounding the cell.
Protein and fats are long molecules with both nonpolar hydrocarbon segments and polar subunits. A protein often folds itself in a way that buries the non-polar units within the molecule and presents the polar subunits to the water that surrounds the protein.
The cell membrane is believed to consist of long-chain phospholipid molecules whose polar ends toward the aqueous medium outside the membrane and whose nonpolar portions are within the membrane.