Consider a 675-mL container at 499 °C in which the pressure of nitrogen is 1.98x106 Pa.
a) What mass of nitrogen (in g) is present in this container?
b) How many molecules is this?
PV = nRT
Solve for n. V must be in L, I would convert Pa to atm and you must convert T in degrees C to Kelvin. Then n = grams/molar mass. Solve for grams.
b)One mole contains 6.022 x 10^23 molecules. Go from there.