question_answer 51)

The air is a mixture of a number of gases. The major components are oxygen and nitrogen with approximate proportion of 20% is to 79% by volume at 298 K. The water is in equilibrium with air at a pressure of 10 attn. At 298 K, if the Henry's law constant for oxygen and nitrogen are 3.30 x 107 mm and 6.51 x 107 mm, respectively, calculate the composition of these gases in water.

Answer:

Step-I. Calculation of partial pressure of oxygen and nitrogen Total pressure of air in equilibrium with water = 10 atm. As air contains 20% oxygen and 79 % nitrogen by volume, Partial pressure of oxygen (PO2)                 = 2 x 760 mm = 1520 mm Partial pressure of nitrogen () = 7.9 x 760 mm 6004 mm Step-II. Calculation of composition of O2 and N2 dissolved in water Applying Henry?s law, Or = 4.61 × 10?5 = 9.22 × 10?5.