How many moles of oxygen gas, o2, are in a storage tank with a volume of 1.000*105 l at stp?

STP means standard temperature and pressure which is equivalent to 273 K and 1 atm, respectively. Assuming ideal gas behavior, the solution for this problem is as follows:

PV = nRT

Solve for n,

n = RT/PV

n = (0.0821 L-atm/mol-K) (273 K) / (1 atm) (1*10⁵ L)

n = 2.24*10⁻⁴ moles