[Fe(H2O)6]3+ is strongly paramagnetic whereas [Fe(CN)6]3– is weakly paramagnetic. Explain.

in presence of CN- the 3d electron pair up leaving only one unpaired electron.the hybridisation is d2sp3 forming inner orbital complex.in the presence of H20 3d electron do not pair up.the hybridisation is sp3d2 forming an outer orbital complex containg five unpaired electron.it is strongly paramagnetic

This is due to the fact that H2o is a weak field ligand which forms high spin complexes. In Zn[Fe(H2o)6] 3+ there are 5 paired electrons whereas in [Fe(CN)6]3- there is only one paired elceron.

Dear student,
In the presence of CN-, the 3d electrons pair up, leaving only one unpaired electron resulting in a hybridisation of d2sp3 forming inner orbital complex. While in the presence of H20 3d electrons do not pair up.and the hybridisation is sp3d2 forming an outer orbital complex containg five unpaired electron. Which is strongly paramagnetic.
Hope it helps.
Thanks and regards,
Kushagra