All questions of The d- and f-Block Elements & Coordination Compounds for JEE Exam

A metal, M forms chlorides in its +2 and +4 oxidation states.
Which of the following statements about these chlorides is correct?
  • a)
    MCl2 is more ionic than MCl4
  • b)
    MCl2 is more easily hydrolysed than MCl4
  • c)
    MCl2 is more volatile than MCl4
  • d)
    MCl2 is more soluble in anhydrous ethanol than MCl4
Correct answer is option 'A'. Can you explain this answer?

Akash Shah answered
Metal atom in the lower oxidation state forms the ionic bond and in the higher oxidation state the covalent bond. because higher oxidation state means small size and great polarizing power and hence greater the covalent character. Hence MCl2 is more ionic than MCl4.

The species having tetrahedral shape is
  • a)
    [PdCl4]2–
  • b)
     [NiCl4]2–
  • c)
    [Pd(CN)4]2–
  • d)
    [Ni(CN)4]2–
Correct answer is option 'B'. Can you explain this answer?

The configuration of Ni2+ is 3d8. For the elements of the first transition series, Cl behaves as a weak field/ high spin ligand. Hence Ni in [NiCl4]2– is sp3  hybridised leading to tetrahedral shape.

In nitroprusside ion the iron and NO exist as FeII and NO+ rather than FeIII and NO. These forms can be differentiated by
  • a)
    estimating the concentration of iron
  • b)
    measuring the concentration of CN
  • c)
    measuring the solid state magnetic moment
  • d)
    thermally decomposing the compound.
Correct answer is option 'C'. Can you explain this answer?

Deepika Sen answered
The forms of iron and NO in nitroprusside ion can be differentiated by measuring the concentration of CN (cyanide) rather than by estimating the concentration of iron.

In nitroprusside ion, the FeII (ferrous) form of iron is coordinated to five CN ligands and one NO ligand. On the other hand, the FeIII (ferric) form of iron is coordinated to four CN ligands and one NO ligand.

By measuring the concentration of CN, one can determine the ratio of FeII to FeIII in the nitroprusside ion. A higher concentration of CN would indicate a higher ratio of FeII to FeIII, while a lower concentration of CN would indicate a higher ratio of FeIII to FeII.

The number of geometric isomers that can exist for square planar complex [Pt (Cl) (py) (NH3) (NH2OH)]+ is
(py = pyridine) :
  • a)
    4
  • b)
    6
  • c)
    2
  • d)
    3
Correct answer is option 'D'. Can you explain this answer?

Ujwal Chawla answered
Square planar complexes of type M[ABCD] form three isomers. Their position may be obtained by fixing the position of one ligand and placing at the trans position any one of the remaining three ligands one by one.

The pair (s) of reagents that yield paramagnetic species is/are
  • a)
    Na and excess of NH3
  • b)
    K and excess of O2
  • c)
    Cu and dilute HNO3
  • d)
    O2 and 2-ethylanthraquinol
Correct answer is option 'A,B,C'. Can you explain this answer?

Aryan Sen answered
Na + NH3 (excess) → Dilute solution of Na in liq.
NH3 → Paramagnetic
K + O2 (excess) → KO2 (O2 is paramagnetic)
Cu + HNO3 (dil.) → Cu(NO3)2 + NO (NO is paramagnetic) 2-Ethylanthraquinol + O2 →
2-Ethylanthraquinone + H2O2
(H2O2 is diamagnetic)

Which kind of isomerism is exhibited by octah edral Co(NH3)4Br2Cl?
  • a)
    Geometrical and Ionization
  • b)
    Geometrical and Optical
  • c)
    Optical and Ionization
  • d)
    Geometrical only
Correct answer is option 'A'. Can you explain this answer?

Anuj Saini answered
Co(NH3)4Br 2Cl will show both geometr ical a n d ionization isomerism. [Co(NH3)4Br2]Cl and [Co(NH3)4BrCl]Br are ionization isomers and geometrical isomers are

Identify the incorrect statement among the following:
  • a)
    4f and 5f orbitals are equally shielded. 
  • b)
    d-Block elements show irregular and erratic chemical properties among themselves.
  • c)
    La and Lu have partially filled d-orbitals and no other partially filled orbitals.
  • d)
    The chemistry of various lanthanoids is very similar.
Correct answer is option 'A'. Can you explain this answer?

Om Singh answered
Incorrect Statement: 4f and 5f orbitals are equally shielded.

Explanation:
- Shielding refers to the reduction in the effective nuclear charge experienced by an electron in an atom due to the presence of other electrons.
- In general, electrons in inner orbitals shield electrons in outer orbitals more effectively than electrons in outer orbitals shield each other.
- The shielding effect decreases as we move from the s orbital to the p orbital, and further decreases from p to d orbitals.
- The 4f and 5f orbitals belong to the f block of the periodic table, and they are located in the innermost part of the atom.
- The 4f orbital is shielded more effectively than the 5f orbital because it is closer to the nucleus and is shielded by the electrons in the 1s, 2s, 2p, 3s, 3p, 3d, and 4s orbitals.
- On the other hand, the 5f orbital is shielded by the electrons in the 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, and 4f orbitals, which are further away from the nucleus.
- Therefore, the 4f and 5f orbitals are not equally shielded, and the statement in option 'A' is incorrect.

Summary:
The incorrect statement among the given options is option 'A' which states that 4f and 5f orbitals are equally shielded. In reality, the 4f orbital is shielded more effectively than the 5f orbital.

The complex ion which has no ‘d’ electron in the central metal atom is
  • a)
    [MnO4]-
  • b)
    [Co(NH3)6]3+
  • c)
    [Fe(CN)6]3 –
  • d)
    [Cr(H2O)6]3+
Correct answer is option 'A'. Can you explain this answer?

In [MnO4], Mn is in +7 oxidation state.
Electronic configuration of Mn (Z = 25) : [Ar] 3d54s2
Electronic configuration of Mn7+  : [Ar] 3d04s0 Central atom in other ions have definite number of d electrons
No. of electrons

Which of the following compounds is metallic and ferromagnetic?
  • a)
    VO2
  • b)
    MnO2
  • c)
    TiO2
  • d)
    CrO2
Correct answer is option 'D'. Can you explain this answer?

Amrita Sarkar answered
Out of all the four given metallic oxides CrO2 is attracted by magnetic field very  strongly. The effect persists even when the magnetic field is removed. Thus CrO2 is metallic and ferromagnetic in nature.

Which pair of compounds is expected to show similar colour in aqueous medium?
  • a)
    FeCl2 and CuCl2
  • b)
    VOCl2 and CuCl2
  • c)
    VOCl2 and FeCl2
  • d)
    FeCl2 and MnCl2
Correct answer is option 'B'. Can you explain this answer?

Colour of transition metal ion salt is due to d-d transition of unpaired electrons of d-orbital. Metal ion salt having similar number of unpaired electrons in d-orbitals shows similar colour in aqueous medium.

Statement-1 : The geometrical isomers of the complex [M(NH3)4Cl2] are optically inactive. and
Statement-2 : Both geometrical isomers of the complex [M(NH3)4Cl2] possess axis of symmetry. 
  • a)
    Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1.
  • b)
    Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1
  • c)
    Statement-1 is True, Statement-2 is False
  • d)
    Statement-1 is False, Statement-2 is True
Correct answer is option 'B'. Can you explain this answer?

Rithika Mehta answered
The geometrical isomers of [M(NH3)4Cl2] can be represented as follows:-
These isomers are optically inactive and they posses axis of symmetry.
Both the statements are thus true. Out of two possible answers i.e. option (a) and (b) option (b) is correct as the statement 2 is not a correct explanation of statement 1.
For a molecule to be optically active it should not possess alternate axis of symmetry.

Statement-1 : Zn2+ is diamagnetic.
Statement-2 : Two electrons are lost from 4s orbital to form Zn2+.
  • a)
    Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1.
  • b)
    Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1
  • c)
    Statement-1 is True, Statement-2 is False
  • d)
    Statement-1 is False, Statement-2 is True
Correct answer is option 'B'. Can you explain this answer?

Tarun Roy answered
Statement-1 : Zn2 is diamagnetic.

Statement-2 : Two electrons are lost from 4s orbital to form Zn2.

To determine the correctness of the statements and whether Statement-2 is a correct explanation for Statement-1, let's analyze the electronic configuration and magnetic properties of Zn2.

Electronic Configuration of Zinc (Zn) :
The atomic number of zinc (Zn) is 30, which means it has 30 electrons. The electronic configuration of zinc is as follows:

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰

Formation of Zn2 :
When zinc loses two electrons, it forms Zn2. The loss of electrons occurs from the highest energy level (outermost shell) first. In the case of zinc, the 4s electrons are lost to form Zn2. The electronic configuration of Zn2 can be represented as:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰

Magnetic Properties of Zn2 :
To determine the magnetic properties of an ion or atom, we need to consider the presence of unpaired electrons.

In the case of Zn2, the electronic configuration shows that all the electrons are paired. There are no unpaired electrons in Zn2. According to Hund's rule, if all the electrons are paired, the substance is diamagnetic.

Conclusion :
Based on the analysis, we can conclude the following:

- Statement-1 is True : Zn2 is diamagnetic because it has all its electrons paired.
- Statement-2 is True : Two electrons are lost from the 4s orbital to form Zn2.
- Statement-2 is NOT a correct explanation for Statement-1 : Statement-2 explains the process of electron loss from the 4s orbital to form Zn2 but does not provide an explanation for the diamagnetic nature of Zn2.

Therefore, the correct answer is option B - Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1.

Coordination compounds have great importance in biological systems. In this context which of the following statements is incorrect ?
  • a)
    Cyanocobalamin is B12 and contains cobalt
  • b)
    Haemoglobin is the red pigment of blood and contains irons
  • c)
    Chlorophylls are green pigments in plants and contain calcium
  • d)
    Carboxypeptidase - A is an exzyme and contains zinc.
Correct answer is option 'C'. Can you explain this answer?

Chlorophylls are green pigments in plants and contain calcium
Chlorophylls are essential pigments in plants responsible for capturing light energy during photosynthesis. However, it is important to note that chlorophylls do not contain calcium. The central atom in the structure of chlorophyll is magnesium, not calcium. This is a common misconception, but the correct information is that chlorophyll contains magnesium at its core, not calcium.

Explanation:
- Chlorophyll is a complex molecule that consists of a porphyrin ring with a magnesium ion at its center. This magnesium ion plays a crucial role in the absorption of light energy in plants.
- The presence of magnesium in chlorophyll allows plants to convert sunlight into chemical energy through the process of photosynthesis.
- Calcium, on the other hand, is not a component of chlorophyll and does not play a direct role in the light-capturing function of this pigment.
- Therefore, the statement that chlorophylls contain calcium is incorrect. The correct information is that chlorophylls contain magnesium.
In conclusion, while coordination compounds such as cyanocobalamin, hemoglobin, and carboxypeptidase contain cobalt, iron, and zinc respectively, chlorophylls do not contain calcium. It is important to have a clear understanding of the composition of biological molecules to appreciate their functions in living organisms.

The octah edral complex of a metal ion M3+ with four monodentate ligands L1, L2, L3 and L4 absorb wavelengths in the region of red, green, yellow and blue, respectively. The increasing order of ligand strength of the four ligands is:
  • a)
    L4 <L3 < L< L1
  • b)
    L1 < L3 < L< L4
  • c)
    L3 < L2 < L< L1
  • d)
    L1 < L2 < L< L3
Correct answer is option 'B'. Can you explain this answer?

Nabanita Basu answered
For a given metal ion, weak field ligands create a complex with smaller Δ, which will absorbs light of longer l and thus lower frequency. Conservely, stronger field ligands create a larger Δ, absorb light of shorter l and thus higher v i.e. higher energy.
So order of ligand strength is
L1 < L3 < L< L4

The complex showing a spin-only magnetic moment of 2.82 B.M. is :
  • a)
    Ni(CO)4
  • b)
    [NiCl4]2–
  • c)
    Ni(PPh3)4
  • d)
    [Ni(CN)4]2–
Correct answer is option 'B'. Can you explain this answer?

Nitya Yadav answered
The correct answer is b) [NiCl4]2.

To determine the spin-only magnetic moment of a complex, we can use the formula:

μ = √(n(n+2)) where n is the number of unpaired electrons.

For a), Ni(CO)4, we need to determine the number of unpaired electrons in the Ni atom. The electron configuration of Ni is 1s2 2s2 2p6 3s2 3p6 4s2 3d8. Since Ni has 8 valence electrons in the 3d shell, it can potentially have 2 unpaired electrons. However, in Ni(CO)4, each CO ligand donates a pair of electrons to the Ni atom, resulting in the formation of a d10 configuration with all electrons paired. Therefore, the spin-only magnetic moment of Ni(CO)4 is 0 B.M.

For b), [NiCl4]2, we need to determine the number of unpaired electrons in the Ni atom. The electron configuration of Ni is 1s2 2s2 2p6 3s2 3p6 4s2 3d8. In [NiCl4]2, each Cl ligand donates one electron to the Ni atom, resulting in the formation of a d8 configuration with two unpaired electrons. Plugging n = 2 into the formula, we get:

μ = √(2(2+2)) = √(2(4)) = √8 = 2.82 B.M.

Therefore, the complex showing a spin-only magnetic moment of 2.82 B.M. is [NiCl4]2.

The spin only magnetic moment value (in Bohr magneton units) of Cr(CO)6 is
  • a)
    0
  • b)
    2.84
  • c)
    4.90
  • d)
    5.92
Correct answer is option 'A'. Can you explain this answer?

Understanding the Magnetic Moment in Cr(CO)6
The magnetic moment of a complex is determined by the presence of unpaired electrons. In the case of Cr(CO)6, we need to analyze its electronic configuration and the effect of the ligands.
Electronic Configuration of Chromium
- Chromium (Cr) has an atomic number of 24.
- Its ground state electronic configuration is [Ar] 3d5 4s1.
- In Cr(CO)6, chromium is in a +3 oxidation state, which results in an electronic configuration of 3d4 (after losing 3 electrons).
CO as a Ligand
- Carbon monoxide (CO) is a strong-field ligand and causes pairing of electrons.
- In an octahedral field created by six CO ligands, the 3d orbitals split into two groups: lower-energy t2g and higher-energy eg orbitals.
Electron Configuration in Cr(CO)6
- The 3d4 configuration under the influence of CO will lead to all four electrons being paired in the t2g orbitals.
- Thus, there are no unpaired electrons in Cr(CO)6.
Calculating the Magnetic Moment
- The spin-only magnetic moment formula is given by the equation: μ = √(n(n+2)), where n is the number of unpaired electrons.
- Since Cr(CO)6 has 0 unpaired electrons (n=0), substituting into the formula gives: μ = √(0(0+2)) = 0.
Conclusion
- Therefore, the spin-only magnetic moment of Cr(CO)6 is 0 Bohr magnetons, confirming that the correct answer is option 'A'.

Consider the following complex ions, P, Q and R.
P = [FeF6]3–, Q = [V(H2O)6]2+ and R = [Fe(H2O)6]2+
The correct order of the complex ions, according to their spin-only magnetic moment values (in B.M.) is
  • a)
    R < Q < P
  • b)
    Q < R < P
  • c)
    R < P < Q
  • d)
    Q < P < R
Correct answer is option 'B'. Can you explain this answer?

The electronic configuration of central metal ion in complex ions P, Q and R are
Higher the no. of unpaired electron(s), higher will be magnetic moment.
Thus the correct order of spin only magnetic moment is  Q < R < P

Among the following ions which one has the highest paramagnetism?
  • a)
    [Cr(H2O)6]3+
  • b)
    [Fe(H2O)6]2+
  • c)
    [Cu(H2O)6]2+
  • d)
    [Zn(H2O)6]2+
Correct answer is option 'B'. Can you explain this answer?

Highest parmagnetic character will be shown by the ion having maximum number of unpaired electrons in their d-subshells.
25Cr3+ has 3 unpaired electrons ; 26Fe2+ has 4 unpaired electrons
29Cu2+ has 1 unpaired electrons ; 30Zn2+ has no unpaired electrons
So (a), (b) & (c) show paramagnetism. Out of which (b) has the highest paramagnetism.

NiCl2 {P(C2H5)2(C6H5)}2 exhibits temperature depend-ent magnetic behaviour (paramagnetic/diamagnetic). The coordination geometries of Ni2+ in the paramagnetic and diamagnetic states are respectively
  • a)
    tetrahedral and tetrahedral
  • b)
    square planar and square planar
  • c)
    tetrahedral and square planar
  • d)
    square planar and tetrahedral
Correct answer is option 'C'. Can you explain this answer?

Sanchita Patel answered
In both states (paramagnetic  and diamagnetic) of the given complex, Ni exists as Ni2+ whose electronic configuration is [Ar] 3d84s0.

In the above paramagnetic state the geometry of the complex is sp3 giving tetrahedral geometry.
The diamagnetic state is achieved by pairing of electrons in 3d orbital.
Thus the geometry of the complex will be dsp2 giving square planar geometry.

PASSAGE 1
The coordination number of Ni2+ is 4.
NiCl2 + KCN (excess) → A (cyano complex)
NiCl2 + Conc . HCl (excess) → B (chloro complex)
Q. Predict the magnetic nature of A and B
  • a)
    Both are diamagnetic
  • b)
    A is diamagnetic and B is paramagnetic with one unpaired electron
  • c)
    A is diamagnetic and B is paramagnetic with two unpaired electrons
  • d)
    Both are paramagnetic
Correct answer is option 'C'. Can you explain this answer?

Rithika Mehta answered
However, CN is a strong field ligand so it forces the 3d electrons to pair up and hence the effective configuration in this case will be Ni2+ in presence of CN

Thus [Ni (CN)4]2– exhibits dsp2 hybridization and square planar shape. Since here number of unpaired electrons is zero the complex will be diamagnetic.
In case of [NiCl4]2–, Cl is a weak field ligand, so the effective configuration of Ni2+ in this complex will be as follows : Ni2+ in presence of Cl
So here Ni2+ is sp3 hybridised and thus tetrahedral in shape. Since the complex has two unpaired electrons, it will be paramagnetic.

Arrange Ce+3, La+3, Pm+3 and Yb+3 in increasing order of their ionic radii.
  • a)
    Yb+3 < Pm+3 < Ce+3 < La+3
  • b)
    Ce+3 < Yb+3 < Pm+3 < La+3
  • c)
    Yb+3 < Pm+3 < La+3 < Ce+3
  • d)
    Pm+3 < La+3 < Ce+3 < Yb+3.
Correct answer is option 'A'. Can you explain this answer?

Aryan Sen answered
In lanthanides there is a regular decrease in the atomic radii as well as ionic radii of trivalent ions as the atomic number increases from Ce to Lu. This decrease in size of atoms and  ions is known as lanthanide contraction.
Although the atomic radii do show some irregualrities but ionic radii decreases from La to Lu. Thus the correct order is.
Yb+3    <   Pm +3  <    Ce +3 < La +3
86.8pm   97pm     1 02pm  103pm

The magnetic moment (spin only) of [NiCl4]2– is :
  • a)
    1.82 BM
  • b)
    5.46 BM
  • c)
    2.82 BM
  • d)
    1.41 BM
Correct answer is option 'C'. Can you explain this answer?

Shail Saha answered
Understanding the Complex: [NiCl4]2–
The magnetic moment of a complex ion is determined by the presence of unpaired electrons. In the case of [NiCl4]2–, we need to analyze the electronic configuration of nickel (Ni) and its interaction with chloride ligands.
Electron Configuration of Nickel
- Nickel has an atomic number of 28.
- The electron configuration is: [Ar] 3d8 4s2.
- In the +2 oxidation state (as in [NiCl4]2–), nickel loses 2 electrons, leading to the configuration: 3d8.
Effect of Chloride Ligand
- Chloride (Cl–) is a weak field ligand and does not cause significant pairing of electrons.
- Therefore, in a tetrahedral complex like [NiCl4]2–, the 3d electrons remain unpaired.
Count of Unpaired Electrons
- For 3d8 configuration in a tetrahedral field:
- The arrangement of electrons will have 2 unpaired electrons.
Calculating the Magnetic Moment
- The formula for magnetic moment (μ) is given by:
μ = √(n(n + 2)), where n is the number of unpaired electrons.
- For [NiCl4]2–, n = 2 (unpaired electrons).
Substituting the Values
- μ = √(2(2 + 2)) = √(2 * 4) = √8 = 2.82 BM.
Thus, the magnetic moment of [NiCl4]2– is 2.82 Bohr Magnetons (BM), confirming that option 'C' is correct.

The most stable ion is
  • a)
    [Fe(OH)3]3-
  • b)
    [Fe(Cl)6]3-
  • c)
    [Fe(CN)6]3-
  • d)
    [Fe(H2O)6]3+.
Correct answer is option 'C'. Can you explain this answer?

Nandini Nair answered
The cyano and hydroxo complexes are far more stable than those formed by halide ion. This is due to the fact that CN and OH are strong lewis bases (nucleophiles).
Further [Fe(OH)5]3– is not formed. hence most stable ion is [Fe(CN)6]3-

The oxidation state Cr in [Cr (NH3)4 Cl2]+ is
  • a)
    0
  • b)
    + 1 
  • c)
    + 2
  • d)
    + 3
Correct answer is option 'D'. Can you explain this answer?

Gayatri Patel answered
Oxidation state of Cr in [Cr (NH3)4 Cl2]+.
Let it be x,  1 × x + 4 × 0 + 2 × (–1) = 1 Therefore x = 3.

The number of moles of KMnO4 that will be needed to react with one mole of sulphite ion in acidic solution is
  • a)
    2/5
  • b)
    3/5
  • c)
    4/5
  • d)
    1
Correct answer is option 'A'. Can you explain this answer?

Charvi Chopra answered
To determine the number of moles of KMnO4 needed to react with one mole of sulphite ion in acidic solution, we need to first write the balanced chemical equation for the reaction between KMnO4 and sulphite ion.

The balanced equation is as follows:
5SO3^2- + 2MnO4^- + 6H+ -> 5SO4^2- + 2Mn^2+ + 3H2O

From the balanced equation, we can see that 2 moles of KMnO4 react with 5 moles of sulphite ion. Therefore, the ratio of moles of KMnO4 to sulphite ion is 2:5.

Now, we can use this ratio to determine the number of moles of KMnO4 needed to react with one mole of sulphite ion.

Let's assume x moles of KMnO4 are needed to react with 1 mole of sulphite ion.

According to the ratio, we can set up the following equation:

2 moles of KMnO4 / 5 moles of sulphite ion = x moles of KMnO4 / 1 mole of sulphite ion

Cross-multiplying and solving for x, we get:

2 * 1 = 5 * x
2 = 5x
x = 2/5

Therefore, the number of moles of KMnO4 needed to react with one mole of sulphite ion is 2/5.

Hence, the correct answer is option A) 2/5.

The geometry of Ni(CO)4 and Ni(PPh3)2Cl2 are
  • a)
    both square planar 
  • b)
    tetrahedral and square planar, respectively
  • c)
    both tetrahedral
  • d)
    square planar and tetrahedral, respectively
Correct answer is option 'C'. Can you explain this answer?

Sahana Ahuja answered
NOTE : In metal carbonyl the metal is in zero oxidation state.
In Ni(CO)4 , O.N. of Ni = 0
For Ni (Z = 28)
In presence of CO two 4s electrons pair up, thus
In Ni(PPh3)2Cl2, O.N. of Ni = +2 For Ni2+
PPh3 and Cl can’t pair up d-electrons, leading to sp3 hybridization leading to tetrahedral geometry.

Statement-1 : [Fe(H2O)5NO]SO4 is paramagnetic. and
Statement-2 : The Fe in [Fe(H2O)5NO]SO4 has three unpaired electrons.
  • a)
    Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1.
  • b)
    Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1
  • c)
    Statement-1 is True, Statement-2 is False
  • d)
    Statement-1 is False, Statement-2 is True
Correct answer is option 'A'. Can you explain this answer?

Akash Shah answered
In [Fe(H2O)5NO] SO4, Let the oxidation state of Fe be x. Then for [Fe(H2O)5 NO]2–,
x + 1 = + 2 or x = + 2 – 1 = + 1
Hence in this complex the oxidation state of Fe is + 1 Electronic configuration of Fe+ can be represented as Fe+ = 1s22s22p63s23p63d7. This unexpected configuration is due to presence of strong ligand field.
Due to which 1 electron from 4s1 gets shifted to 3d– orbitals.
The 3d7 electrons in five 3d– orbitals can be shown as
In it we find 3 unpaired electrons.
Because of the presence of unpaired electrons the complex is paramagnetic i.e. statement 1 is true.
As is clear from above there are three unpaired electrons in this complex i.e. statement 2 is true.
Since paramagnetic behaviour is due to presence of unpaired electrons in it so statement 2 is correct explanation of statement 1.
In view of the above facts the correct answer is option (a)

The color of KMnO4 is due to :
  • a)
    L → M charge transfer transition
  • b)
    α - α* transition
  • c)
    M → L charge transfer transition
  • d)
    d – d transition
Correct answer is option 'A'. Can you explain this answer?

Avantika Joshi answered
L → M charge transfer spectra. KMnO4 is colored because it absorbs light in the visible range of electromagnetic radiation. The permanganate ion is the source of color, as a ligand to metal, (L → M) charge transfer takes place between oxygen's p orbitals and the empty d-orbitals on the metal. This charge transfer takes place when a photon of light is absorbed, which leads to the purple color of the compound.

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