Explain CuSO4.5H2O is blue while ZnSO4 and CuSO4 are colourless?
Water acts as a ligand in CuSO4.5H2OCuSO4.5H2O , causing crystal field splitting. As a result, in CuSO4.5H2OCuSO4.5H2O , a d—d transition is possible and visible. Due to the lack of water in anhydrous CuSO4CuSO4 and ZnSO4ZnSO4 , ligand crystal field splitting is not feasible, and hence no colour is produced.
