1
MCQ (Single Correct Answer)

### JEE Main 2018 (Online) 16th April Morning Slot

Which of the following complexes will shows geometrical isomerism ?
A
aquachlorobis (ethylenediamine) cobalt (II) chloride
B
pentaaquachlorohromium (III) chloride
C
potassium amminetrichloropltinate (II)
D
potassium tris(oxalato) chromate (III)

## Explanation

(a)   [Co(H2O) Cl(en)2]Cl  $\to$  it shows gemetrical isomerism.

(b)   [Cr(H2O)5Cl]Cl2  :   This complex is [MA5B] type. It does not show geometrical isomerism.

(c)   K[Pt(NH3)Cl3]  :  Thiscomplex is [MAB3] type. It does not show geometrical isomerism.

(d)   K3[Cr(OX)3]  :  This complex is [M(AA)3] type. It does not show geometrical isomerism.
2
MCQ (Single Correct Answer)

### JEE Main 2019 (Online) 9th January Morning Slot

Two complexes [Cr(H2O)6]Cl3 (A) and [Cr(NH3)6]Cl3 (B) are violet and yellow coloured, respectively. The incorrect statement regarding them is :
A
$\Delta$0 values of (A) and (B) are calculated from the energies of violet and yellow light, respectively
B
both are paramagnetic with three unpaired electrons
C
both absorb energies corresponding to their complementry colors.
D
$\Delta$0 value for (A) is less than that of (B).

## Explanation

NH3 is a strong field ligand.

H2O is weak field ligand.

Let $\Delta$violet is the crystal field splitting energy of complex A and $\Delta$yellow is for complex B.

$\therefore$   $\Delta$yellow > $\Delta$violet.

We know, $\Delta$ = ${{hc} \over {{\lambda _{absorb}}}}$

Violet color will absorb yellow color and yellow color will absorb violet color.

$\therefore$   $\Delta$yellow = ${{hc} \over {{\lambda _{violet}}}}$

and $\Delta$violet = ${{hc} \over {{\lambda _{yellow}}}}$

So, $\Delta$o of A is calculated from energy of yellow light and $\Delta$o of B is calculated from energy of violet light.
3
MCQ (Single Correct Answer)

### JEE Main 2019 (Online) 9th January Evening Slot

The complex that has highest crystal field splitting energy ($\Delta$), is :
A
[Co(NH3)5(H2O)]Cl3
B
K2[CoCl4]
C
[Co(NH3)5Cl]Cl2
D
K3[Co(CN)6]

## Explanation

As complex K3[Co(CN)6] have CN$-$ ligand which is strongfield ligand amongst the given ligands in other complexes.
4
MCQ (Single Correct Answer)

### JEE Main 2019 (Online) 9th January Evening Slot

Homoleptic octahedral complexes of a metal ion 'M3+' with three monodenate ligands L1, L2 and L3 adsorb wavelenths in the region of green, blue and red respectively. The increasing order of the ligands strength is :
A
L3 < L1 < L2
B
L3 < L2 < L1
C
L1 < L2 < L3
D
L2 < L1 < L3

## Explanation

Stronger the ligand, absorption of light having lower wavelength is more.

Order of $\lambda$ : Red $>$ Green $>$ Blue

Hence, ligand strength is L3 $<$ L1 $<$ L2

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