You breathe in 12.0 l of pure oxygen at 298 k and 1,000 kpa to fill your lungs. how many moles of oxygen did you take in. can you also show me how to solve this ?

Your question must be at 1.000kPa not 1,000KPa... That's ~10Atms, or 10x atmospheric pressure we as humans are used to breathing... So the following calculation is for 1.000kPa or 0.987Atms. => 0.482 mole O₂(g). If your problem is at 1,000kPa then multiply mole answer by 10.

Explanation:

Using the Ideal Gas Law PV = nRT solve for n = PV/RT

n = moles of O₂(g)

P = Pressure = 1.000KPa = 0.987Atm

V = Volume in liters = 12L

R = Universal Gas Constant = 0.08206 L·Atm/mol·K

T = Temperature in Kelvin = 298K

n = P·V/R·T = (0.987Atm)(12L)/(0.08206 L·Atm/mol·K)(298K) = 0.482 mole O₂(g)