At 37 c and 760 mm hg pressure, 0.023 ml of o2 can be dissolved in 1 ml of plasma, whereas at the same temperature and pressure, 0.510 ml of co2 will dissolve in 1 ml of plasma. what explains the difference

On dissolving CO2 in plasma, some of it reacts with water to produce carbonic acid which gets dissociates to produce proton and bicarbonate ion with negative charge.  

The pKa1 value indicates the acidic nature of carbonic acid and its value is 3.6. this value indicates the spontaneous nature of this reaction in alkaline solutions and helps in proceeding the reaction in forward direction. This results in dissolving of large amount of CO2 in plasma whereas Oxygen does not go any reaction f this type. Oxygen is a non polar molecule, so its solubility is quite lower in plasma.

Thus, CO2 is more soluble in plasma than O2