Ka1, Ka2 and Ka3 are the respective ionisation constants for the following reactions

H2 S ⇋ H+ + HS-


HS ⇋ H+ + S2-


H2S ⇋ 2H+ + S2-


The correct relationship between Ka1 , Ka2 and Ka3 is


For the reaction : H2 S ⇋ H+ + HS-


the ionization constant -


(i)


o For the reaction : HS ⇋ H+ + S2-


the ionization constant -


(iii)


From this two above reaction, we can get the following reaction (addition)


H2S ⇋ 2H+ + S2-


Then Ka1 and Ka2 will also be added and Ka3 will be the result :



From equation (i) and (ii) x (here addition means the multiplication of the Equilibrium constants)


1