Why do chemists use the mole as a counting unit?

• A. Because it represents the mass of a single atom or molecule.
• B. Because it is equal to one gram of any substance.
• C. Because it is the smallest possible unit of matter.
• D. Because it allows chemists to count atoms, molecules, or ions in practical amounts by relating them to a measurable quantity of substance.

Answer: (D)

Verified step by step guidance

1. Understand that atoms, molecules, and ions are extremely small and numerous, making it impractical to count them individually in a laboratory setting.
2. Recognize that the mole is a counting unit in chemistry, similar to how a dozen counts 12 items, but a mole counts \$6.022 \times 10^{23}$ particles (Avogadro's number).
3. Know that the mole links the microscopic world (atoms and molecules) to the macroscopic world by relating the number of particles to a measurable amount of substance in grams.
4. Realize that using the mole allows chemists to measure out amounts of substances that contain a specific number of particles, facilitating calculations in chemical reactions and stoichiometry.
5. Therefore, chemists use the mole because it provides a practical way to count and work with atoms, molecules, or ions by connecting their number to a measurable mass.