We assume that N2 is an ideal gas thus we use the ideal gas equation in order to solve for the number of moles of N2. The ideal gas equation is expressed as : PV = nRT. The calculations are as follows:
(300 x 10^3) Pa x (2.5 x 10^-4) mL = n x 8.314472 Pa.m3/(mol.K) x 300 K
n = 0.0300 mol N2
