First, you convert liters to moles. Usually you have to go to grams but this is STP.
Get moles directly by dividing the 4 by STP (22.4) [tex] \frac{4}{22.4} =0.17857142857[/tex] About [tex]1.8*10^{-1} [/tex] or 0.18 moles whichever your teacher prefers
