Monday, October 7, 2013

Find the magnetic moment of the complex

Question: Consider the following complex ions, P, Q and R 
P = [FeF6]3-, Q = [V(H2O)6]2+, and R = [Fe(H2O)6]2+
What is the correct order of the complex ions, according to their spin-only magnetic moment values (in B.M.)?

A) R<Q<P
B)  Q<R<P
C)  R<P<Q
D) Q<P<R

Solution:

The formula used to calculate the spin-only magnetic moment can be written as:

μ= n(n+2) B.M.

Where n = no. of unpaired electron

 

So first let us find out number of unpaired electron in each complex.

 

1)   P = [FeF6]3-

Charge on Fe in the complex: [FeF6]3-    

                                                                                     X + (1x6) = -3

                                                        = +3

So number of unpaired electron in Fe+3 = 3s2, 3p6, 3d5, 4s0            

                                                                      = 5

Magnetic moment = 5 (5+2)

                                         =35 B.M.

 

2)   Q = [V(H2O)6]2+

Charge on Fe in the complex: X + (0x6) = +2

                                                 = +2

So number of unpaired electron in V+2 = 3s2, 3p6, 3d3,           

                                                                     = 3

Magnetic moment = 3 (3+2)

                                         =15 B.M.

 

3)   R = [Fe(H2O)6]2+

Charge on Fe in the complex: X + (0x6) = +2

                                                    = +2

So number of unpaired electron in Fe+2 = 3s2, 3p6, 3d6         

                                                                     = 4

Magnetic moment = 4 (4+2)

                                         =24 B.M.

So the correct order of the complex ions, according to their spin-only magnetic moment values is P > R > Q


Thus option B is correct. 

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