2.6 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.

It is given that the solubility of H2S in water at STP is 0.195 m, i.e., 0.195 mol of H2S is dissolved in 1000 g of water.

Moles of water=1000 g18 g mol-1=55.56 mol

Mole fraction of H2S, x=Moles of H2SMoles of H2S+Moles of water

=0.1950.195+55.56

=0.0035

At STP, pressure (p) = 0.987 bar

According to Henry’s law:

p = KHx

KH=px
=0.9870.0035bar

= 282 bar