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

In order to find the pressure, we will use the ideal gas equation which is:

PV = nRT

n is the number of moles. By definition,

moles = mass (m) / molecular weight (Mr)

So, we may substitute the previous equation for "n" in the ideal gas law. Rearranging the equation and substituting (remember to convert kg into grams and the temperature into Kelvin),

P = mRT/VMr

P = (4.04 x 10³ * 0.082 * (273 + 23)) / (50 * 32)

P = 61.3 atm

The pressure of the oxygen gas is 61.3 atm