What does Avogadro's law state about equal volumes of gases at the same temperature and pressure?

• A. Equal volumes of gases at the same temperature and pressure contain the same number of particles.
• B. The volume is independent of the number of particles.
• C. The mass of gas determines its volume at fixed conditions.
• D. The temperature determines the number of particles.

Answer: (A)

At fixed temperature and pressure, the amount of gas dictates how much space it takes up in a given volume. Avogadro’s law states that equal volumes of different gases contain the same number of particles. So, when two gases occupy the same volume at the same temperature and pressure, they have the same number of molecules, even if their masses or identities differ. This explains why one mole of any gas occupies the same volume under those conditions.