A 250 mL sample of nitrogen (N2) has a pressure of 745 mm Hg at 30 C. What is the mass of nitrogen?

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