kH, the Henry's Law constant, for oxygen (O2) in water is 769.2 Latm/mol at 298K. Furthermore we know that air at sea level (1 atm.) is 21% oxygen.
Calculate the mass of O2 in grams dissolved in a fishing pond whose volume is 5 x 107 liters when the temperature is 298K and atmospheric pressure of air is 1 atm.