The phrase “like dissolves like” refers to the fact that polar solvents dissolve polar solutes and nonpolar solvents dissolve nonpolar solutes. Gases can only dissolve other gases. Condensed phases can only dissolve other condensed phases. Polar solvents dissolve nonpolar solutes and vice versa. Solvents can only dissolve solutes of similar molar mass.
The Correct Answer and Explanation is:
Correct Answer:
The phrase “like dissolves like” refers to the fact that polar solvents dissolve polar solutes and nonpolar solvents dissolve nonpolar solutes.
Explanation
The phrase “like dissolves like” is a guiding principle in chemistry that describes how solubility is influenced by molecular polarity. This concept is particularly important in solutions, where one substance (the solute) dissolves in another (the solvent). The “like” in this phrase refers to the polarity of molecules—whether they are polar or nonpolar.
Polar substances have molecules with partial positive and partial negative charges due to unequal sharing of electrons. Water is a classic example of a polar solvent because of its bent molecular shape and electronegative oxygen atom. On the other hand, nonpolar substances consist of molecules where electrons are shared equally, and there is no permanent charge separation. Examples include oils and hydrocarbons like hexane.
Polar solvents are effective at dissolving polar solutes because of strong dipole-dipole interactions or hydrogen bonding. These interactions help break apart the solute particles and incorporate them into the solvent. For instance, table salt (NaCl), an ionic compound, dissolves in water due to strong interactions between water molecules and the ions.
Nonpolar solvents dissolve nonpolar solutes through London dispersion forces (induced dipole-induced dipole interactions). Since neither the solute nor the solvent has a permanent charge, these temporary interactions are sufficient to allow solubility. For example, iodine dissolves well in carbon tetrachloride, a nonpolar solvent.
Other statements such as “gases can only dissolve other gases” or “solvents can only dissolve solutes of similar molar mass” are incorrect. Gases can dissolve in both liquids and solids, and solubility depends more on intermolecular forces than on molar mass.
In conclusion, solubility depends primarily on the intermolecular forces between solute and solvent molecules. When these forces are similar, the substances are more likely to mix, hence the principle: like dissolves like.
