Answer
91.22 atm
Work Step by Step
We are given the mass of Oxygen in kg so we must first convert this to moles to be able to use the ideal gas law. The molar mass of O2 is 2 * 16 = 32 g/mol.
This means we have:
0.29kg * (1000g/1kg) * (1mol/32g) = 9.0625 moles
We are told the volume is 2.3L and the temperature is 9C (we add 273 to find Kelvin) or 282K. We can then use ideal gas law to find the pressure:
PV = nRT so P = nRT/V = (9.0625 moles * 0.0821 * 282K) / 2.3L = 91.22 atm