Question

1) why color of Zn EDTA complex is colourless?
2) what is meant by masking?

Answer 1

1) The Zn EDTAcomplex is colorless due to the fact that the energy of the quantum of electromagnetic radiation, which is necessary for making the transition between the split d-orbitals, lies outside the visible range.

2)Masking of the anion is the binding of the ion into a complex that is more stable than the titrating complex and indicator. If the ion is masked, it will almost not affect the titration.