Class 12th

5. (A) (i) Out of all the elements of the first transition series copper has the highest second ionisation enthalpy.

Electronic configuration of Copper is: 3d¹⁰4s¹

After the Loss of first electron from the 4s copper acquires 3d¹⁰ configuration which is stable. Therefore, removal of second electron from the field 3-D orbital is very difficult and requires high amount of energy.

(ii) Among the elements of first transition series zinc has the highest third ionisation enthalpy. Electronic configuration of zinc is: 3d¹⁰4s²

After the loss of two electrons from 4s orbital, Z and +2 Ion acquires 3d¹⁰ fully filled configuration which is highly stable therefore removal of third electron from 3d 10orbital will be more difficult and requires a large amount of energy.

(iii) Zinc is the element of the first transition series that has the lowest enthalpy of atomisation. The electronic configuration of zinc is: 3d¹⁰4s².This is because it has filled 3d-subshell and filled 4s-subshell so no unpaid electron is available for metallic bonding.

(B) (i) CarbonylmM (CO)₅

Ans: Fe (CO)₅ as per EAN Rule. 

EAN Rule: Effective atomic number (EAN), number that represents the total number of electrons surrounding the nucleus of a metal atom in a metal complex. 

(ii) MO₃F

Ans: The M in the given complex is in +7 O.S.

4. (a) As per fajan's rule, smaller the size of ion, greater is its tendency to make covalent bonds as the positively charged cation strongly attract the negatively charged electron cloud.

On moving from La to Lu in the lanthanoid series, the atomic size decreases so the covalent character increases. Hence, La₂O₃ is ionic and Lu₂O₃ is covalent.

(b) The stability of Oxo salts is directly proportional to the size of atom, as we move from La to Lu, the size of the atom decreases and hence the stability of oxo salts also decreases.

(c) As we move along the lanthanide series, the atomic size decreases. As a result, the charge/size ratio increases and the stability of the complexes also increases.

(d) As an effect of lanthanide contraction, zirconium and hafnium have similar radius of 160pm and 159 pm respectively. Due to this similarity in their size, they show similar physical and chemical properties. Lanthanoid contraction: Because the elements in Row 3 have 4f electrons.

These electrons do not shield good, causing a greater nuclear charge. This greater nuclear charge has a greater pull on the electrons and result in the decrease in their size and atomic radii.

(e) Acidic or basic character of oxides is related to the nature of oxides. As we move along the lanthanide series from La to Lu, the covalent character increases. 

Therefore, their basic character decreases or acidic character increases. 

3. (A)  =  MnO₂

(B)  = K₂MnO₄

(C)  =  KMnO₄ 

(D)  =  KIO₃ 

2MnO₂ +  4KOH  + O₂ → 2K₂MnO₄ +  2H₂O

  (A)                                              (B)

3MnO₄^2-  +  4H⁺  → 2MnO₄^-  +  MnO₂ +  2H₂O

  (C)

2MnO₄^2-  +  2H₂O  +  KI→ 2MnO₂ +  2SO₄^-  +  KIO₃

  (A)                         (D)  

2.  (A)  =  FeCr₂O₄

(B)  =  Na₂CrO₄

(C)  =  Na₂Cr₂O₇

(D)  = K₂Cr₂O₇ 

4FeCrO₄ +  8NaCO₃ +  7O₂ → 8Na₂CrO₄ +  2Fe₂O₃ +  8CO₂

  (A)                                                     (B)

2NaCrO₄ +  2H +  → Na₂Cr₂O₇ +  2Na +  + H₂O

Na₂Cr₂O₇ +  KCl→ K₂Cr₂O₇ +  2NaCl 

  (C)                            (D)  

1. CuCO₃ CuO  +  CO₂

  (D) 

Ca (OH)₂ +  CO₂ → CaCO₃ + H₂O

  (E) 

CaCO₃ +  CO₂ + H₂O → Ca (HCO₃)₂

                                        clear sol. 

CuO   +  CuS 3Cu  +  SO2 

  (A)  

 Cu + 4HNO3 → Cu (NO3)2 + 2NO2 +  2H2O

           (conc.)           (B) 

Cu (NO₃)₂ +  4NH₃ →  [Cu (NH₃)₄] (NO₃)₂

                                    (C) blue solution 

74. Option (ii) Assertion and reason both are correct statements, but reason is not correct explanation for assertion is the answer since in graphite carbon atoms are arranged in different layers and each atom is covalently bonded to three of its neighbouring atoms in the same layer due to which the fourth valence electron of each atom, present between the different layers is free to move and this makes graphite a good conductor of electricity.

As different layers can slide over each other which makes it soft. while in case of diamond C atom is bonded covalently with their adjacent atoms throughout the crystal. Thus, all the four valencies are satisfied. Covalent bonds are strong and directional in nature ; therefore, atoms are held very strongly at their positions. This is why diamond is hard and has a very high melting point but decomposes before melting, also acting as an insulator.