<prompt> CO2 diffuse more easily than O2 because: Less denseLess denseMore soluble in plasmaLess molecular weight of CO2Less pCO2 in the alveoli  <response>: B i.e. More soluble in plasma - Carbon dioxide CO2 is 20 times more soluble in water plasma than oxygen 02, this is the reason why CO2 diffuses about 20 times more rapidly than does 02 across the alveolar-capillary barrier although CO2 has a higher but not very different molecular weight than 02 . Rate of diffusion a solubility VMW - Because the transfer of carbon monoxide CO across blood gas barrier of lung is limited solely by diffusion, and therefore CO is the gas of choice for measuring the diffusion propeies of lunge. 