Question

What is the pressure of a 50.0L tank that contains 4.04kg of oxygen, O2 at 23 degrees C

Answer 1

It has low temperature, so you can use ideal gas equations PV=nRT, where P is in Kpa, V in liter or m^3,n are moles of the gas(4.04kg*1000 to grams divided by molecular wight of O2), R is the gas constant(look it up on wikipedia with the right units) and T is temperature in K. you can use any unit you want, only check if they match

Answer 2

solve for P and you got it