Advanced Placement (AP) Chemistry Practice Exam

Potassium chloride (KCl) is likely to be an ionic compound due to the nature of the elements involved. Ionic compounds are formed when there is a significant difference in electronegativity between the two bonding atoms, typically between metals and nonmetals. In KCl, potassium (K) is a metal that tends to lose an electron to achieve a stable electron configuration, while chlorine (Cl), a nonmetal, tends to gain an electron to complete its valence shell. As potassium loses an electron, it becomes a positively charged ion (K⁺), and as chlorine gains that electron, it becomes a negatively charged ion (Cl⁻). The electrostatic attraction between these oppositely charged ions results in the formation of an ionic bond, characteristic of ionic compounds.

In contrast, other choices contain only covalent bonds or no ionic character. Carbon dioxide (CO2) consists of covalent bonds between carbon and oxygen, methanol (CH3OH) also has covalent bonds throughout its structure, and ozone (O3) consists of covalent bonds between oxygen atoms. Therefore, KCl stands out as the only compound among the choices that is likely to be ionic, due to the presence of a metal and a nonmetal