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Pressure of dilute gases

Substances can be brought into gaseous form. If the gas is dilute or hot enough, or both, all substances show the same behavior (ideal gas). If we fill such a gas into a container of given volume at a prescribed temperature, the following is observed. It takes different masses for different substances to obtain the same pressure. For example, 2 g of hydrogen gas, 71 g of chlorine, or 32 g of oxygen gas all have the same pressure if volume and temperature are the same.

Interpretation

According to what we know from reactions, 2 g of hydrogen gas, 71 g of chlorine, or 32 g of oxygen are equal amounts of the three substances. Therefore, the pressure of simple gases depends upon the amount of substance of the gas, not upon its mass or some other possible measure. In the particle model, it takes equal numbers of particles to get the same pressure for the same volume and temperature.