How many molecules does 4.48L of hydrogen contain? Why do we find V (H2) -? And where did 22.4 come from

We find the number of hydrogen molecules by the following formula.
N = Na × n.
Where Na is Avogadro’s number of 6.02 × 10 ^ 23.
First, we find n (the amount of substance).
We apply the following formula.
n = V / Vm.
Where n is the amount of substance.
V is the volume of the substance.
Vm is the molar volume of the substance, which has a constant value of 22.4 L / mol.
n = 4.48 L / 22.4 L / mol = 0.2 mol.
Next, we find the number of molecules.
N = 0.2 mol × 6.02 × 10 ^ 23 = 1.204 × 10 ^ 23 molecules.
Answer: N = 1.204 × 10 ^ 23 molecules.