A scheme for the removal of H2S from a gas stream by scrubbing with water at 293 K and 1.013×105 Pa is being considered. The liquid will initially contain 3.7 mol % H2S. It is desired that the exiting gas stream contains only 0.2 mol % H2S. The absorbing water will enter at the top of the tower that is H2S free. At the given temperature and pressure of the system, the equilibrium of H2S-water will obey Henry's law according to the following relationship:
YH2S = 48.3 XH2S
a. For a countercurrent absorber, determine the moles of water that are required per mole of H2S-free carrier gas if 1.5 times the minimum ratio will be used.
b. Determine the composition of the exiting liquid.