The d- and f- Block Elements Test - 8

CuCl₂ is used as catalyst in Deacon’s Process.

The filling of 4f before 5d orbital results in a regular decrease in atomic radii called Lanthanoid contraction which essentially compensates for the expected increase in atomic size with increasing atomic number. The net result of the lanthanoid contraction is that the second and the third d series exhibit similar radii and have very similar physical and chemical properties much more than that expected on the basis of usual family relationship.

Annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase it's ductility and reduce it's hardness, making it more workable. It involves heating a material above it's recrystallisation temperature, maintaining a suitable temperature for a suitable amount of time, and then cooling.

Mercurous chloride is known as calomel (Hg₂Cl₂).

Silver ornaments turns black coming in contact with H₂S due to formation of Ag₂S. The chemical equation for this change can be represented as given below:
2Ag(s) + H₂S(g) → Ag₂S(s) + H₂(g)

HgCl₂ + 4KI → K₂[HgI4] + 2KCl

Atomic number of Fe is 26 and it's electronic configuration is [Ar] 3d⁶ 4s². When we remove 3 electrons, it becomes [Ar] 3d⁵.

Chromate ion (CrO₄^2-) changes to dichromate ion (Cr₂O₇^2- ) on acidification.
2 CrO₄^2- + 2 H⁺ → Cr₂O₇^2- + H₂O

Fe₄[Fe(CN)₆]₃ is Prussian Blue. The intense blue colour of Prussian blue is associated with the energy of the transfer of electrons from Fe(II) to Fe(III). Many such mixed-valence compounds absorb certain wavelengths of visible light resulting from intervalence charge transfer.