In both the complexes, Fe is in +3 oxidation state with the configuration 3d⁵. CN- is a strong ligand. In its presence, 3d electrons pair up leaving only one unpaired electron. The hybridization is d 2sp³forming inner orbital complex. H₂0 is a weak ligand. In its presence, 3d electrons do not pair up. The hybridization is sp³ d²  forming an outer orbital complex containing five unpaired electrons. Hence, it is strongly paramagnetic.

CuCl₂ is more stable due to more hydration energy.

KMnO₄ is kept in dark bottles because KMnO₄ gets decomposed to K₂MnO₄ in presence of sunlight.

It is because CO can form σ (sigma) as well as π -bond, therefore, it is stronger ligand than CI^-.

In Actinoids 5f, 6d and 7s orbitals have comparable energies and electrons from these orbitals can take part to show higher oxidation states.

Double salts dissociate completely into their constituent simple ions when dissolve in water, i.e they lose their identity in aqueous solution
e.g KCl.MgCl₂.6H₂O ⟶ K⁺+Ma²⁺+3Cl^-+6H₂O
While coordination compounds do not dissociate into simple ions, i.e. they retain their identity both in solid state and in aqueous solutions.
(ii) The IUPAC name of the following given complexes are:
(a) K₃[Fe(C₂O₄)₃]
Potassiumtrioxalatoferrate (III)
(b) [Pt(NH₃)₆]Cl₄: Hexaammineplatinum (IV) chloride
(iii) The structure of cis-isomer of [Co(NH3))4Cl₂]⁺ ion is.

In aqueous solution, CO₂ reacts as follows:
\({ CO }_{ 2 }+{ H }_{ 2 }O\rightleftharpoons { H }_{ 2 }{ CO }_{ 3 }\rightleftharpoons { H }^{ + }+HCO_{ 3 }^{ - }\)
In the presence of H⁺ ion, \(MnO^{ 2- }\) ion undergoes disproportionation to form \(MnO^{ - }_{ 4 }\)   ion (purple in colour) and MnO₂ (brown solid).

It is because in tetrahedral complexes, the orbital splitting energies are not very large, therefore, forced pairing does not take place, unpaired electrons are sufficiently large forced pairing of electrons, therefore, low spin complexes are not formed.

(i) [Co(NH₃)₄(H₂O)Cl]Cl₂
(ii) K₂[Zn(OH)₄]
(iii) K₃[Al(C₂O₄)₃]
(iv) [CoCl₂(en)₂]⁺
(v) [Ni(CO)₄]

Cr²⁺ has electronic configuration 3d⁴ Chromium also shows +3 and +6 oxidation states. Fe²⁺ has electronic configuration 3d⁶. Iron has oxidation states +2 and +3.

(i) (a) Haemoglobin
(b) Chlorophyll
(ii) Applications of complex compounds.
(a) They are used in photography, Le. AgBr forms soluble complex with sodium thiosulphate rn photography.
(b) K[Ag(CN)₂] is used for electroplating of silver, K[Au(CN)₂] is used for gold plating.
(c) Some of ligands oxidise Co²⁺ to Co³⁺ ion.
(d) EDTA is used for estimation of Cla²⁺ and Mg²⁺ in hard water.
(e) Silver and gold are extracted by treating zinc with their cyanide complexes.
(f) Ni²⁺ is tested and estimated by DMG (dimethylglyoxime).

(ii) Potassium

(i) (a) Vanadium
(b) Iron
(c) Silver
(ii) \(\begin{equation} 2 \mathrm{MnO}_{4}^{-}+5 \mathrm{H}_{2} \mathrm{~S}+16 \mathrm{H}^{+} \longrightarrow 2 \mathrm{Mn}^{2+}+5 \mathrm{~S}+8 \mathrm{H}_{2} \mathrm{O} \end{equation}\)

(i) The transition elements exhibit variable oxidation states. The variable oxidation states of transition metals are due to the participation of ns and (n - 1) d-electrons. This is because of the very small difference between the energies of (n - 1) d and ns orbitals. For the first five elements, the minimum oxidation state is equal to the number of electrons ---in the 4s orbitals and the other oxidation states are equal to the sum of 4s and some of the 3d-electrons. The highest oxidation state is equal to the sum of 4s and 3d electrons. For the remaining elements, the minimum oxidation state is equal to electrons in 4s-orbitals and the maximum oxidation state is not equal to the sum of 4s and 3d electrons. In general, the oxidation state increases up to the middle and then decreases.

\({ \triangle }_{ t }=\left( \frac { 4 }{ 9 } \right) { \triangle }_{ 0 }\).  Thus,  \({ \triangle }_{ t }\) is smaller than \({ \triangle }_{ 0 }\).  Hence, less energy (higher wavelength) is absorbed by tetrahedral complexes than by octahedral complexes of the same metal and ligands.  Therefore, the observed colour are different.

(i) As isomer A reacts with AgNO₃ to give a white precipitate, CI must be present in the ionization sphere. As it does not react with BaCI₂, SO₄^2- must be present in coordination sphere.
Formula of A = [Co(NH₃)₅SO₄] CI (coordination no. of Co = 6) As reactions are reverse for isomer B, formula of B = [Co(NH₃)₅CI]S0₄
(ii) Ionization isomerism.
(iii) A = Pentaarnminesulphatocobalt (III) chloride ; B = Pentaamminechloridocobalt (ill) sulphate