Which statement correctly describes the quantities that can be determined if the number of moles of a substance is known?

• A. The mass, number of particles, and volume (at STP) can all be calculated.
• B. Only the mass of the substance can be calculated.
• C. Only the volume of a solid can be calculated.
• D. Only the number of atoms in a molecule can be determined.

Answer: (A)

Verified step by step guidance

1. Understand that the number of moles of a substance is a fundamental quantity in chemistry that relates to the amount of substance present.
2. Recall that the mass of a substance can be calculated from moles using the molar mass: \(\text{mass} = \text{moles} \times \text{molar mass}\).
3. Recognize that the number of particles (atoms, molecules, or formula units) can be found using Avogadro's number: \(\text{number of particles} = \text{moles} \times 6.022 \times 10^{23}\).
4. Know that for gases at standard temperature and pressure (STP), the volume can be calculated using the molar volume of a gas: \(\text{volume} = \text{moles} \times 22.4\ \text{L}\).
5. Conclude that if the number of moles is known, you can calculate the mass, the number of particles, and the volume (for gases at STP), making the first statement correct.