Reaction of Cr3+

Its colour is green. A solution of Cr3+ is commonly provided in form of CrCl3(aq). In that case the solution is blue-violet rather than green this is caused by the environment of Cl and hydrolysis

Test Observations Notes
Add NH3 an immediate green ppt soluble in xs is formed Cr(OH)3(s)
Add solid sodium carbonate Effervescence, gas which tunrs limewater milky is produced.Solution turns to grey-green. A pake green ppt is also formed Solution of Cr3+(aq) is acidic and so reacts witha carbonate to produce CO. Green ppt is Cr(OH)3(s)
Add NaOH(sq) an immediate grey-green ppt is formed whichis soluble in xs NaOH to form a dark green solution Grey-green ppt is Cr(OH)3(s). The ppt reacts with further xs OH ions in a ligand exchange reaction forming a dark green complex [Cr(OH)6]3+
Add NaOH(aq) followed by 20Vol Hydrogen peroxide. Solution truns yellow Cr3+ oxidized to CrO42-


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