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I was reading about Avogadro's law which states that

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?

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  • $\begingroup$ 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. $\endgroup$
    – Mauricio
    Feb 8, 2022 at 19:34
  • $\begingroup$ Vaporize two molar masses of the "solid gas", say ice and nitrogen. In a vacuum chamber. Suck out the gasses and equate them? $\endgroup$ Feb 8, 2022 at 19:41
  • $\begingroup$ @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. $\endgroup$
    – Silica19
    Feb 8, 2022 at 19:53
  • $\begingroup$ No, set them to the same pressure verifying it with a manometer. $\endgroup$
    – Mauricio
    Feb 8, 2022 at 20:16
  • $\begingroup$ @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. $\endgroup$
    – Silica19
    Feb 8, 2022 at 20:20

2 Answers 2

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Prepare different gases, each on a container with a piston and a barometer. Fill the containers at constant temperature with the same number of moles for each gas. Modify the height of the piston until they all reach the same pressure. The volume in each container should now be the same.

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  • $\begingroup$ your argument is circular, if you want to verify avogadro's law using experiments, you must not assume that you know what a mole of certain gas weighs $\endgroup$ Oct 31, 2023 at 4:41
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Gather two solids of one mono atomic or mono molecular stuff (for example, nitrogen ice and normal ice). Take a molar weight of each. Put them in an empty balloon and heaten both up. Let all solid vaporize and compare the size of the balloons.

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