The “spin-only” magnetic moment[in units of Bohr magneton, (µ_B)] of Ni²⁺ in aqueous solution would be(At. No. Ni = 28)

6
1.73
2.84
4.90

Solution

he value of the ‘spin only’ magnetic moment for one of the following configurations is 2.84 BM. The correct one is

d⁵(in strong ligand field)
d³(in weak as well as in strong fields)
d⁴(in weak ligand fields)
d⁴(in strong ligand fields)

Solution

A chemist wants to determine the molecular geometry of the [CoCl₄]^2– ion. Which of the following gives the best suggestion for a measurement and for the interpretation of that measurement?

Using absorption spectroscopy, measure λ_max then calculate Δ_O for octahedral geometry
Measure the molecule’s magnetic moment and use the result to estimate the number of unpaired spins in the molecule. If this number is low,the geometry is likely to be square planar; otherwise, it is likely to be tetrahedral
Measure the molecule’s magnetic moment and use the result to estimate the number of unpaired spins in the molcule.If this number is low, the geometry is likely to be tetrahedral; otherwise,it is likely to be square planar
Measure the molecule’s magnetic moment and use the result to estimate the number of unpaired spins in the molecule. If this number is low, the geometry is likely to be tetrahedral; otherwise, it is likely to be octahedral

Solution

In the complexes of C.N. 4, square planar geometry gives rise to low spin(spin paired)configurations whereas tetrahedral complexes display high spin configurations.

Which one of the following cyano complexes would exhibit the lowest value of paramagnetic behaviour ?

(At.Nos : Cr = 24, Mn = 25, Fe = 26, Co = 27)

[Co(CN)₆]^3-
[Fe(CN)₆]^3-
[Mn(CN)₆]^3-
[Cr(CN)₆]^3-

Solution

[Cr(H₂O)₆]Cl₃(at.no. of Cr = 24) has a magnetic moment of 3.83 B. M. The correct distribution of 3d electrons in the Chromium of the complex is

Solution

Atomic number of Cr and Fe are respectively 25 and 26,which of the following is paramagnetic?

[Cr(CO)₆]
[Fe(CO)₅]
[Fe(CN)₆]_–4
[Cr(NH3)₆]⁺³

Solution

Cr³⁺ has 4s° 3d³ electronic configuration with 3 unpaired electrons, hence paramagnetic. In other casespairing of d-electrons take place in presence of strongfield ligands such as CO or CN^-.

In Cr(CO)⁶ molecule 12 electrons are contributed by CO group and it contain no odd electron