How many moles are in 68.5 liters of oxygen gas at STP?

We can solve this problem when we use the conditions of a gas at standard temperature and pressure. It has been established that at STP where the temperature is 0 degrees Celsius and the pressure is 101.325 kPa, the volume of 1 mole of gas is 22.4 L. We will use this data for the calculations.

68.5 L (1 mol O2 / 22.4 L O2) = 3.06 mol O2