Coordinated water molecules if Cd(II) complex can be successively replaced by Br finally to resultin [CdBr4]-2. In this process the fourth equilibrium constant is observed which is higher than one because:
1
Equilibrium for the last step is always the highest
2
Three molecules of water are released during the fourth step
3
The aqua-Cd(II) species is octahedral
4
The Br- anion replaces a neutral H2O molecule from the coordinationsphere.