Question

$CuS{O}_4.5H_{2}O$ is blue is colour while anhydrous $CuS{O}_4$ is colourless due to:

• A. Presence of strong field ligand in $CuS{O}_4.5H_{2}O$
• B. Due to absence of water(ligand), d-d transitions is not possible in $CuS{O}_4$
• C. anhydrous undergoes d-d transition due to crystal field splitting
• D. colour is lost due to unpaired electrons

Answer 1

The correct option is B Due to absence of water(ligand), d-d transitions is not possible in $CuS{O}_4$

In $CuS{O}_4.5H_{2}O$ water acts as ligand and causes crystal field splitting. This makes d-d transition possible. On the other hand, in $CuS{O}_4$ due to absence of ligand crystal field splitting is not possible, Hence no colour is observed.