In my textbook, the derivation of Dalton's Law of Partial Pressure is done by keeping the volume of a mixture of gas in a container constant which is equal to the volume of container itself.
How can this be so? Let's say we have 100 moles (fairly large) of Nitrogen and 1 mole of hydrogen gas taken in a container of a certain volume. Then is the volume still considered equal to that of the container in this case? Because this is what is done when deriving Dalton's law of partial pressure?
Also, if we have 100 moles of a gas and another just a single molecule then what happens?