Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

What type of bond is formed between two molecules of water?

1. An ionic bond

2. A hydrogen bond

3. A metallic bond

4. A disulfide bond

The correct answer is: A hydrogen bond

The correct answer is the formation of a hydrogen bond between two molecules of water. In a water molecule, the oxygen atom is more electronegative than the hydrogen atoms, which means it attracts the shared electrons more strongly. This creates a partial negative charge on the oxygen atom and a partial positive charge on the hydrogen atoms. When two water molecules are in proximity, the positive hydrogen atom of one molecule can be attracted to the negative oxygen atom of another water molecule. This attractive force is what constitutes a hydrogen bond. Hydrogen bonds play a critical role in many of water's unique properties, such as its high surface tension, its ability to dissolve many substances, and its relatively high boiling and melting points compared to other small molecules. The other types of bonds mentioned do not apply in the context of interactions between water molecules. Ionic bonds involve the transfer of electrons from one atom to another, typically between a metal and a non-metal, while metallic bonds involve a sea of delocalized electrons found in metals. Disulfide bonds, on the other hand, are covalent bonds formed specifically between the sulfur atoms of cysteine residues in proteins. Therefore, the emphasis on hydrogen bonding is essential to understand the molecular interactions in water.