The solubility of oxygen gas in water at 25 °c and 1.0 atm pressure of oxygen is 0.041 g/l. the solubility of oxygen in water at 2.5 atm and 25 °c is

According to Henry's law, solubility is proportional to the external pressure. Since both cases in the problem have the same temperature, only the pressure varies from 1.0 atm to 2.5 atm. This means that just as the pressure is multiplied by a factor of 2.5, we can multiply the solubility by a factor of 2.5 as well. This gives us 0.041 g/L * 2.5 = 0.1025 g/L.