Question

There is a point at which volume cannot be decreased any further for a sealed container of gas

Answer 1

Avogadro's law states that, equal volumes of all gases, at the same temperature and pressure, have the same number of molecules. If you change the size of the container without adding or subtracting molecules you will end up changing either the temperature or the pressure of the gas, or both. This is because PV = NkT where N is the number of molecules, P the pressure, V the volume of the container, k A constant, and T the temperaturee of the gas. So you can’t change V if you don’t change P, T or N.