The equilibrium concentration of oxygen in fresh water exposed to the atmosphere is given for two temperatures. At 15 degrees celcius equilib [O2]= 630μmol/L at 25 degrees celcius equiln [O2]= 517μmol/L

The expression for the equilibrium constant, K, between the oxygen in the gas phase and in solution is given by K=[O2]/PO2/atm. Where pO2 is the partial pressure of atmospheric oxygen.

I need to calculate the enthalpy of dissolution, I figured I need to use the integrated Vant hoff equation.

But how do I figure out the partial pressues of oxygen so I can calculate the equilibrium constants? I know that P= xa x P^*

[Thank you