What volume would 3.01•1023 molecules of oxygen gas occupy at STP?

First, find moles of oxygen gas: (3.01 x10^23 molec.) / (6.02 x10^23) = 0.5mol O2

Second, multiply moles by the standard molar volume of a gas at STP: (0.5mol) (22.4L) = 11.2L O2