Which law states that the volume of gas is directly proportional to the number of moles at constant pressure and temperature?

Avogadro's Law is the principle that states the volume of a gas is directly proportional to the number of moles of the gas when temperature and pressure are held constant. This relationship can be expressed mathematically as V ∝ n, where V represents volume and n represents the number of moles. The implications of this law highlight that for a given gaseous substance, as the number of moles increases, the volume must also increase, assuming no changes in temperature and pressure conditions. This provides foundational support for understanding gas behavior in various chemical reactions and physical processes.

The other laws mentioned have different relationships. Boyle's Law relates pressure and volume when temperature is constant, Charles' Law deals with volume and temperature at constant pressure, and Gay Lussac's Law connects pressure and temperature at constant volume. Each of these laws describes specific interactions among gas properties, which helps to clarify the unique focus of Avogadro's Law on the relationship between volume and moles.