Why does carbon dioxide diffuse easier through the bilipid layer than oxygen?
After diffusion the partial pressure of both O2 and CO2 in arteries become almost equal to the atmospheric values(100mmHg and 40mmHg), regardless of partial pressures in veins. Rate of diffusion through membrane is roughly the same, it's the solubility that is different, as CO2 is about 22 times more soluble than O2 (it can be stored is water as HCO3-). 
  However, oxygen still can easily enter and stay inside the blood vessel because it's bound to hemoglobin inside the erythrocyte. Hence there is no significant difference between the diffusion rates.