stp represents the standard temperatures and pressure ( temp of 273 kelvin and pressure of 1 atm). At s.t.p one mole of a gas occupies a volume of 22400 Cm3 or ml. Therefore, we can determine the number of moles of hydrogen gas that will occupy a volume of 500 ml.
number of moles = 500 ml ÷ 22400 ml = 0.02232 moles.
Therefore, the number of moles equivalent to a volume of 500 ml of hydrogen are 0.02232 moles.
