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Molar volume is the volume of one mole of an ideal gase (under standard pressure and temperature) equal to 22.4 liters.

"Equal volumes of different gases at the same temperature and pressure contain the same number of particles" (Avogadro´s law). The number of particles in 24 l at room temperature and usual pressure equals
 1 mol = 6x10²³.
That means that 24 ml air and 24 ml hydrogen in the vial contained 1/1.000 mol = 6x10²⁰ particles.