The air separation unit is an important energy-consuming unit in the process of ammonia synthesis. For the ammonia process with pure oxygen gasification, the purity of oxygen products in the air separation unit is generally 99.6%. If the oxygen purity from the air separation is reduced properly, its energy consumption will decrease effectively, and the energy consumption of the whole ammonia process may further decrease, as the nitrogen element is needed for ammonia synthesis. However, with the increase of the flow rate, the operating cost of the subsequent unit would increase, so there is an optimal purity that could minimize the energy consumption of the whole process. An ammonia-air mixture containing 10% ammonia is sent to an absorber in which 90% of ammonia is absorbed. (a) What is the mole fraction of ammonia in the gas leaving? (b) Express the composition of the exit gas from the absorber in weight percent. (c) What is the average molecular weight of the gas entering and leaving the column? (Average molecular weight of air is 29.