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.


According to Henry's law,


"At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid."


Stated as,


p = KHx


Where,


P = partial pressure of the solute above the solution


KH = Henry's constant


x = concentration of the solute in the solution


Given,


Solubility of H2S in water at STP is 0.195 m


We know,


At STP pressure p = 0.987 bar.


0.195 mol of H2S is dissolved in 1000g of water


Moles of water =


= 55.56 g/mol


the mole fraction of H2S =


=


= 0.0035


According to Henry's law,


p = KHx


KH =


KH =


KH = 282 bar


The Henry’s law constant is 282 bar


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