You have to be careful with the “N” ( normal temperature (20’C)) and STP ( standard 0’C, in degrees Kelvin (273.15) for the equation). One is for convenience, the other is for accuracy. The “22.4L/mol” figure is handy and useful, but based on the conditions at STP, not NTP.
Start with the Ideal Gas Law:
Rearranging the Ideal Gas Law equation we have
where R = 0.0820575 L-atm/K-mol , P = 1.0 atm, n = 1 mol and T = 0’C = 273.15’K (STP)
At NTP this would be
That’s a 10% difference from the STP value!
Directly calculated for this problem, we have:
Applying Avogadro's Number to this we obtain: