What is the concentration of O2 in a fresh water stream in equilibrium with air at 30oC and 2.0 bar? Given, KH (Henry's law constant) of O2=2.0×10-3 mol/kg bar at 30oC.

In this case, KH has been given in the unit of mole/kg bar. Thus, solubility of O2 (or concentration) =KHpgasχO2 (in air)= 0.21∴pO2=pair χO2=1×0.21 bar∴ Solubility =2.0×10-3 molkg bar×0.21 bar                           =0.42×10-3×32 g/kg                           =13.44×10-3 g/kg