CEE 4310 WATER QUALITY ENGINEERING SPRING 2009 HOMEWORK #2 (DUE MAR 5) 1. (40 pts). A wastewater at temperature 20oC and pH 10.0 containing 10 g of NH4Cl (MW = 53.5) is stored in an enclosed reactor for further treatment. The volume of wastewater (VL) is 10 Liter and the container is placed in a closed room with total empty volume (VG) of 10 m3, which is filled with air. The lid of container was accidentally removed and ammonia evaporated into air. Assume that ammonia concentration was initially zero in the air. Also assume that water is well buffered such that pH of the solution does not change due to evaporation of NH3. Dimensionless Henry’s law constant (m) for ammonia (NH3) at 20oC is 0.00056 and equilibrium constant for NH4+↔NH3+ H+is Ka= 10-9.3. (a) (30 pts). express the concentration of ammonia in gas phase (CG) at equilibrium (i.e., steady-state) in terms of m, pH, CT,0(where CT= [NH3] + [NH4+], and subscript 0 denotes initial concentration), VG, VL, and Ka.
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