48. Although zirconium belongs to 4d transition series and hafnium to 5d transition series even then they show similar physical and chemical properties because

(A) Both belong to d-block

(B) Both have same number of electrons

(C) Both have similar atomic radius

(D) Both belong to the same group of the periodic table

Electronic configuration of

Gd is ; Gd₆₄ = [Xe]4f⁷ 5d¹ 6s²

Hence $G{d}_{64}^{++}=\left[Xe\right]4f^{7}5d^{1}6s^0$

Total number of electrons in 4f sub-shell = 7

Ans. = 7

Molecular formula of Mohr’ salt, FeSO₄. (NH₄)₂SO₄.6H₂O.

Molecular formula of potash alum = K₂SO₄.Al₂ (SO₄)₃.24H₂O. Overall molecular formula of potash alum = KAl (SO₄)₂. 12H₂O. Ratio of water molecules in Mohr’ salt and Potash alum

$=\frac{6}{12}=\frac{1}{2}=0.5=5\times 10^{-1}$       

Ans. = 5

Cu₂Cl₂ + Water -> Insoluble

AgCl + Water -> Insoluble

ZnCl₂ + Water -> Colouless solution

CuCl₂ + Water -> Coloured solution due to 3d⁹ electronic configuration.

Nucleophilicity is directly proportional to the electron density of atom and inversely proportional to its electronegativity.

According to Ellingham diagram, the metal oxide with lower $\Delta G^o$ is more stable than metal oxide of higher $\Delta G^o$ at same temperature.