We can use the ideal gas equation based on the assumption that O₂ behaves similar to an ideal gas.
PV = nRT
P-pressure, V- volume, n - number of moles, R - universal gas constant and T - temperature
number of O₂ moles - 48.0 g/ 32 g/mol = 1.5 mol
temperature - 25 °C + 273 = 298 K
substituting the values
P x 5.2 x 10⁻³ m³ = 1.5 mol x 8.314 Jmol⁻¹K⁻¹ x 298 K
P = 714.7 kPa