We can use the ideal gas law equation to find the number of moles of nitrogen at STP
PV = nRT
Where
P - standard pressure - 1 atm
V - 18.65 L
n - number of moles
R - universal gas constant - 0.0821 L.atm/mol.K
T - standard temperature -273 K
Substituting the values in the equation
1 atm x 18.65 L = n x 0.0821 L.atm/mol.K x 273 K
n = 0.832 mol
There are 0.832 mol of Nitrogen gas in the container