How many moles of hydrogen gas are contained in 21.3 l at stp?

To get the moles of hydrogen gas, we will use the molar volume equation, where 1 mole of any ideal gas occupies a volume of 22.4 L. This was derived using the ideal gas law equation;

PV=nRT , where

P - Pressure of the gas

V - Volume occupied by the gas 

n - number of moles of gas present

R - universal gas constant, usually given as 0.0821atm⋅Lmol⋅

T - absolute temperature of the gas

STP conditions are defined as a pressure of 1 atm and a temperature of 273.15 K.

PV=nRT