H2S, a toxic gas with rotten egg like smell, is used for the qualitative analysis. If the solubility of H2S in water at STP is 0.195 m, calculate Henry’s law constant.
Solution -
Since, Solubility = 0.195 molal i.e. 0.195 moles of H2S in 1 Kg of solvent
Therefore, moles of solvent = w/mm = 1000/18 = 55.55
Therefore, Mole fraction of H2S = 0.195 / (0.195+55.55) = 0.0035
Pressure at STP = 1 bar
Therefore, from the Henry's Equation
P(H2S) = Kh x mole fraction of H2S
Kh = 1/0.0035 = 285.71