# How is Avogadro's law tested practically?

Equal volumes of all gases under the same conditions of temperature and pressure contain equal number of molecules.

My question is, how can one verify this practically?

The way that I think we can test this is by filling different types of gases in containers with specific volume at a specific temperature such that the pressure in each is the same, and then calculating the mass of each gas filled to solve for the number of moles.

But how do we test this the other way around, i.e., testing that different gases have equal volumes for a given temperature, pressure and number of moles?

I don't understand how would one be able to calculate the volume of a gas in doing such a test; say for testing at normal temperature (20°C) and pressure (1 atm), one would release the different gases into the atmosphere, but how would one calculate their volumes?

• The question in the title is slightly technical. However, your second question seems trivial, feel the balloons with gases of same temperature, pressure and number of moles and you will see that they occupy the same volume. Feb 8, 2022 at 19:34
• Vaporize two molar masses of the "solid gas", say ice and nitrogen. In a vacuum chamber. Suck out the gasses and equate them? Feb 8, 2022 at 19:41
• @Mauricio In this case, you assume that putting $n$ mole(s) of different gases at same temperature in each balloon results in the same pressure. Feb 8, 2022 at 19:53
• No, set them to the same pressure verifying it with a manometer. Feb 8, 2022 at 20:16
• @Mauricio Setting the pressure to be the same involves adding/removing gas to/from the balloon, thus the no. of moles are not exactly the same in each balloon. Feb 8, 2022 at 20:20