how many moles are present in 11.0 L of neon gas at stp

Answer 1

No need to use density or the ideal gas law or even the molar mass of neon. All you need to know is that at STP (standard temperature and pressure) 1 mole of any ideal gas = 22.4 L. Using this value, we can find moles of neon in 11.0 L @ STP...

11.0 L x 1 mol Ne / 22.4 L = 0.491 moles

Answer 2

You can use the density of Neon gas at STP (0.90 g/L) and the atomic weight of Neon (20.18 g/mol) to find the moles.