Answer is: pressure of oxygen is 31,3 kPa. The total pressure<span> of an ideal gas mixture is the sum of the </span>partial pressures<span> of the gases in the mixture. p(mixture) = p(helium) + p(oxygen) + p(carbon dioxide). p(oxygen) = p(mixture) - (p(helium) + p(carbon dioxide)). p(oxygen) = 101,4 kPa - (68,7 kPa + 1,4 kPa). p(oxygen) = 101,4 kPa - 70,1 kPa. p(oxygen) = 31,3 kPa.