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

Avogadro's Law states that, under constant temperature and pressure, the volume of a gas is directly proportional to the number of moles of that gas. This means that if you increase the number of moles of gas, the volume will also increase, provided that temperature and pressure do not change. This relationship is foundational in understanding gas behavior and is crucial for calculations involving gases, such as in stoichiometry and ideal gas law applications.

The reason this law is significant is that it indicates a fundamental property of gases: that they occupy a certain amount of space based on the quantity of gas molecules present. This law allows chemists to predict how gases will react and behave when the amount of gas changes, which is essential for both practical applications in laboratories and theoretical calculations in chemistry.