D-Block

• [Cu(H2O)6]2+ (Pale blue, octahedral)

  + NH3

  = [Cu(NH3)4(H2O)2]2+ (Royal blue, octahedral)

  + HCl

  = [CuCl4]2- (Yellow-green, tetrahedral)
• [Co(H2O)6]2+ (Pink, octahedral)

  +HCl

  = [CoCl4]2- (Blue, tetrahedral)
• Cr3+ is amphoteric
• • (small amount NaOH) Cr3+ + 3OH- = Cr(OH)3 (Grey-green precipitate)
  • (Excess NaOH) Cr(OH)3 + 3OH- = [Cr(OH)6]3- (Green solution)
• Fe2+, Fe3+ and Cu2+ are not amphoteric.
• Fe2+ + 2OH- = Fe(OH)2 (Dark green precipitate)
• Fe3+ + 3OH- = Fe(OH)3 (Red-brown precipiate)
• Cu2+ + 2OH- = Cu(OH)2 (Pale blue precipitate)
• 2Cu2+ + 4I- = 2CuI (white solid) + I2 (Brown solution)