Two moles of nitrogen gas are contained in an enclosed cylinder with a movable piston.If the molecular mass of nitrogen is 28.0,how many grams of nitrogen are present?
A)0.140
B)56.0
C)42.0
D)112

Question

Quizplus · Accepted Answer

One mole of any gas at standard temperature and pressure (STP) occupies 22.4 liters. Therefore, two moles of nitrogen gas at STP will occupy 44.8 liters. Since the cylinder is enclosed, the volume is constant. Thus, using the Ideal Gas Law, we can solve for the number of grams of nitrogen present:
PV = nRT
(1 atm)(44.8 L) = (2 mol)(0.08206 L atm/mol K)(273 K)
P = (2 mol)(0.08206 L atm/mol K)(273 K)/(44.8 L) = 2.00 atm
n = PV/RT = (2.00 atm)(44.8 L)/(0.08206 L atm/mol K)(273 K) = 1.992 mol
mass = n x molecular mass = (1.992 mol)(28.0 g/mol) = 55.776 g (rounded to 56.0 g, the closest option)

Two Moles of Nitrogen Gas Are Contained in an Enclosed