How many molecules are present in 33.0 L of neon gas at STP

8.87 * 10^23 molecules of Ne

Explanation:

STP means standard temperature and pressure which is 0 degree Celsius and 1 atm. There's a law that says at STP 1 mole of any gas at occupies 22.4 liters of volume. We are gonna use this to do our conversion.

33.0 L Ne * 1mol Ne/22.4L Ne = 1.47321428571 mol Ne (this is moles of Neon)

Now we know avogadro number says there's 6.022*10^23 molecules in 1 mole of anything so we use this to convert the previously calculated moles of Neon to moleculues.

1.47321428571 mol Ne * 6.022*10^23 molecules/1mol Ne = 8.87 * 10^23 molecules of Ne