For this question, we will be using the Ideal Gas Law and the formula that represents this concept, that put together many concepts of gases, the formula is:
PV = nRT
Where:
P = pressure, which will be 2 atm
V = volume, 50 L
n = number of moles, we are trying to find it
R = the constant of gases, which in our case will be 0.082
T = temperature, 300 K
Now we add these values into the formula:
2*50 = n*0.082*300
100 = 24.6n
n = 4.06 moles of Nitrogen will be needed.