Which statement best explains why water is known as a universal solvent?
A. The attractive force between polar water molecules and nearby nonpolar molecules is strong.
B. The attractive force between polar water molecules and other nearby water molecules is strong.
C. The attractive force between polar water molecules and nearby nonpolar molecules is weak.
D. The attractive force between polar water molecules and other nearby water molecules is weak.
The Correct Answer and Explanation is:
The correct answer is:
B. The attractive force between polar water molecules and other nearby water molecules is strong.
Explanation:
Water is often called a “universal solvent” because it has the ability to dissolve a wide range of substances. This property is primarily due to the polar nature of water molecules and the strong intermolecular forces they create, particularly hydrogen bonds.
Water molecules are polar, meaning they have a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. This polarity allows water to interact with various solutes, especially other polar or charged molecules, facilitating dissolution. The term “universal solvent” comes from this ability to dissolve many types of substances, including salts, sugars, acids, and gases.
Key Factors Contributing to Water’s Solvent Abilities:
- Polarity and Hydrogen Bonding: The strong attractive forces between the partial positive charge of the hydrogen atoms in one water molecule and the partial negative charge of the oxygen atoms in another water molecule form hydrogen bonds. These hydrogen bonds are relatively strong, which makes water a very effective solvent for other polar and ionic compounds. For example, when salt (NaCl) dissolves in water, the positive sodium ions are surrounded by the oxygen atoms of water molecules, and the negative chloride ions are surrounded by the hydrogen atoms of water molecules.
- Solubility of Polar and Ionic Compounds: The strong hydrogen bonding in water helps it dissolve ionic compounds and other polar molecules by surrounding and stabilizing the ions or polar molecules, breaking the ionic lattice or polar structure apart. For example, in the case of sodium chloride, the water molecules surround the Na+ and Cl- ions, separating and stabilizing them in solution.
- Cohesion and Adhesion: Water molecules also exhibit cohesion (attraction between water molecules) and adhesion (attraction between water molecules and other substances). These properties allow water to move through capillary action, dissolving substances along the way.
The key to water’s role as a universal solvent lies in its strong ability to interact with other molecules, driven by the strong attractive forces between water molecules themselves, which enables it to dissolve a wide variety of substances.