We assume that nitrogen gas sample here is an ideal gas. So that, we can use the ideal gas equation which is expressed as follows:
PV = nRT
First, we calculate the number of moles from the equation above. Then, use molar mass to calculate mass.
n = PV/RT
n = (745/760) (0.250) / 0.08206 (30+273.15)
n = 0.01 mol
m = 0.01 ( 28) = 0.28 g
