Now, before we use the formula, let's let's realize why we're using 760 mmhg. So the total pressure above our system is the air that we're breathing in is the pressure of the air that we're breathing in. And the air we're breathing in is at atmospheric pressure. And atmospheric pressure is one ATM or 760 mercury. So defined partial pressure of oxygen, we simply multiply mole fraction by our total pressure and we get 159.6 mmhg for oxygen and 600.4
mmhg for nitrogen. So second step is to find the Molarity.