Question

The aqueous solutions of the transition metal salts are acidic as a result of hydrolysis of their hydrated cations. The H2O in these hydrated cations can form different colors in the solution of colmplex ions by entering ligand exchange reaction with different ligands like CI, NH3 SO Cu2+ Fe2+ Cr3+ Ni2+ Co2+ Mn2+ Al3+ V3+ Sc3+ salts are separately a)Write down water-solubility / hydration reactions. b)Write down the hydrolysis reactions and explain the reason for the acidity according to the reaction. c)Sort the cations with their causes according to their acidity strength. d)Concentrated HCl and then concentrated NH3 are added to the aqueous solutions of these transition metal salts, respectively. Accordingly, write down all complex formation reactions occurring by specifying color changes. What can be the causes of ligand changes and different color formations?

Answer 1

Reactions la) Hydration Cu? + 6 H₂O 2+ 2+ [Cu(H₂O). Fe 2+ + 6HO 3+ Cr 3 + 6M20 2+ 2 کی 2+ + 6H₂O 2+ co + 6H₂O [Fe (4,0), 134 [cr CH₂O)]3+ [Ni(H20), ) [co (H2O)]²+ [mm (140), 13+ (ALONO)]3+ (v (120)]3+ [Sc (H2O)]3+ 2+ Mn + 6H₂O 3+ AI + 6420 3+ + 6H₂O 3+ Sc Gи, о + (b) Hydrolysis Reactions + 2+ 2H + 2H₂O + + 2H2O Culor), + felow) Irlow), Fe 2+ Cr3 2H 3+ + + 3 H₂O 3 H + + Ni 2+ + 2H₂O Nilonz 그년 2+ (clon + 2H 2120 + 2+ mn + + 2H+ 3+ A 34+ + 3+ Зн V + 2H₂O muloh) + 340 Allon), + VlOH), + Зн, о 34.0 Sclona + from the reactions given above, released which increase the acidity of the solution 3+ 34+ Sc + we can see that Ht ions are ICS Scanned with CamScann

higher ( 3+ 60*, mn 3+ 5 (1) If a transition metal has a charge of +2 it is acidic. According to this, Salts of Cu2+, Fe2+ pre acidic in nature. has do configuration so it is not considered transitional metal. But it is also acidic. AI is amphoteric in nature. to be a Sc 3+ 3+ 2-+ Id) (aq) HU > No Reaction 2+ (u (aq) + 4NH [ (AH)3 (9) light blue Dark blue +2HC fe (aq) Fe?t (29) feu [Fe(NH3),] 2 + 6NH3 (+ 3+ (aq) + 3HU 3+ (aq) + 6NH 2+ 2HU -> (aq) + Ni 2+ (aq) + 6NH3 green (02+ (aq) Cra, {Cv (NH3)s ] 3+ Nich [Ni(NH3)]2+ blue Coll (lo (NW) 7 2+ + DHU Co2+ (aq) + ONI pink Mn 24 mustard Mrch Reaction + 2.HU + 3 HU Mn2+ (aq) + 6NH A13+ (aq) A13+ (aq) + NH₂ Sc 3+ (og) + AIG, > Al(OH), + Sca, [Sc(MHz)]3+ HU Sc 3+ (9) + NH3

In ligand exchange reactions, one ligand is substituted by another ligand without any change in oxidation state of the metal centre. Different ligands have different strength and thus affect the energy of d orbital of central metal atom in different ways. strong ligands cause more splitting and thus more energy difference for a d-d transition. this causes the colour of the complex to change. Two major causes of colour in complexes is d-d transition and ligand to metal charge transfer.