1)

Which one of following complex has the  highest magnitude of crystal field splitting energy ($\triangle _{0}$)?


A) $[Co(H_{2}O)_{6}]^{3+}$

B) $[Co(NH_{3})_{6}]^{3+}$

C) $[Co(C_{2}O_{4})_{3}]^{3-}$

D) $[CoF_{6}]^{3-}$

Answer:

Option B

Explanation:

 The crystal  field splitting , i.e, $\triangle _{0}$ , depends

upon the field produced by the ligand and charge on the metal ion.

 So, ligands can be arranged in a series  in the order of increasing field strength  . This  series known  as spectrochemical series

eg.  IΘ<BrΘ  <SCNΘ <ClΘ  <FΘ <OHΘ < C2O42-

 $<H_{2}O $ < NCSΘ < EDTA 4- <$NH_{3}$  < en < CNΘ    <CO $\because$

Among the given options , ligand ($NH_{3}$) has highest magnetic field therefore , it has maximum value for  $\triangle _{0}$. 

Hence option (b) is the correct answer