Experiment 2 Colorful Solutions of Iron

orbital energy Color of Fe 3+ -complex & Fe 2+ -complex (spherical field)(octahedral field)(free ion)  o energy is moderated by ligands.  o will influence the complex absorb energy from visible light. λ absorbed versus color observed. crystal field stabilization energy (  o ) c: velocity of light λ: wavelength of light cation: transition metal anion: ligand

Color Change of Fe 2+ (aq) 、 Fe 3+ (aq) ： Fe 3+ (aq)Fe 2+ (aq) A: KSCN(aq)FeSCN 2+ (aq)× B: K 4 Fe(CN) 6 (aq)Fe 4 [Fe(CN) 6 ] 3 (s)K 2 Fe[Fe(CN) 6 ](s) C: K 3 Fe(CN) 6 (aq)Fe[Fe(CN) 6 ](aq)Fe 4 [Fe(CN) 6 ] 3 (s) D: BaCl 2 (aq)FeCl 3 (aq)FeCl 2 (aq) + BaSO 4 (s) E: tannic acid(aq)Fe 3+ -tannate(s)Fe 2+ -tannate(aq) F: oxalic acid(aq)Fe(C 2 O 4 ) 3 3  (aq)FeC 2 O 4 (s) G: NaOH(aq)Fe(OH) 3 (s)Fe(OH) 2 (s) H: Na 2 S(aq)FeS(s)

Reduction of Fe 3+ (aq) by Sn 2+ (aq) ： Sn 2+ (aq) + 2Fe 3+ (aq)  Sn 4+ (aq) + 2Fe 2+ (aq) ΔE° = V Oxidation of Fe 2+ (aq) by Ce 4+ (aq) ： Ce 4+ (aq) + Fe 2+ (aq)  Ce 3+ (aq) + Fe 3+ (aq) ΔE° = V ceric ammonium nitrate ((NH 4 ) 2 Ce(NO 3 ) 6 ) tin(II) chloride (SnCl 2 )

Fe(s) + NaOH(aq)  ？ Fe(s) + H 2 SO 4 (aq)  ？ Another test ： Fe 2+ (aq) + K 3 Fe(CN) 6 (aq)  ？ Acid-base reaction of bulk Iron ：

 Iron gall ink (Dark blue ink): A purple-black or brown-black ink made from Fe 2+ solution and tannic acid.  Ink-bleaching reagent (Ink discoloring solution) Oxalic acid has stronger interaction for binding with Fe 2+ ion than tannic acid. Oxalic acid can be employed as ink discoloring solution to remove the stain formed when iron contact with tannic acid on the paper.

Apparatus & Materials magnetic stirrer with heating function electronic balance test tubes beaker (50 mL) graduated cylinder (25 mL) staple (bulk iron) paper

 potassium thiocyanate ( KSCN)  potassium ferrocyanide ( K 4 Fe(CN) 6 )  potassium ferricyanide (K 3 Fe(CN) 6 )  barium chloride (BaCl 2 )  tannic acid  oxalic acid  sodium hydroxide (NaOH)  sodium sulfide (Na 2 S)  ferric chloride (FeCl 3 )  tin(II) chloride (SnCl 2 )  sulfuric acid (H 2 SO 4 )  ceric ammonium nitrate ( (NH 4 ) 2 Ce(NO 3 ) 6 )  ammonium iron(II) sulfate ((NH 4 ) 2 Fe(SO 4 ) 6 ) Chemicals ：

5.0 mL H 2 SO mL NaOH 1 drop of2~3 drops of10 drops of Colorful Solutions of Iron (evenly shake) (observe ) 1 drop of2~3 drops of 10 drops of (evenly shake) (observe ) ddH 2 O (heating to graduation 5) ddH 2 O 3 drops of dilute H 2 SO 4(aq) 0.6 g of tannic acid ddH 2 O 3 drops of Arabian gum (aq) (stir for dissolving ) Iron gall ink (Dark blue ink) (after dry) ddH 2 O oxalic acid (observe ) 10 drops of K 3 Fe(CN) 6(aq) A. Color change of Iron (III) B. Color change of Iron (II) staple (bulk iron) C. Acid-base reaction of bulk Iron D. Iron gall ink (Dark blue ink) E. Ink-bleaching reagent (Ink discoloring solution)

A: B: C: D: E: F: G: H: Results ： (A) Color change of Iron (III) 1. add FeCl 3(aq), observe the change in test tubes, then record the results

A: B: C: D: E: F: G: H: (A) Color change of Iron (III) 2. add SnCl 2(aq), observe the change in test tubes, then record the results

A: B: C: D: E: F: G: H: (B) Color change of Iron (II) 1. add (NH 4 ) 2 Fe(SO 4 ) 2(aq), observe the change in test tubes, then record the results

A: B: C: D: E: F: G: H: (B) Color change of Iron (II) 2. add (NH 4 ) 2 Ce(NO 3 ) 6(aq), observe the change in test tubes, then record the results

(C) Acid-base reaction of bulk Iron (D) Iron gall ink (E) Ink-bleaching reagent 1. 2.

The Experiment of Next week: The Determination of Vitamin C in Juice (Estimation of Vitamin C in juice by titration) ※ Remember to bring the scientific calculator and the juice without pulp! Suggestion: lemon juice, orange juice Apple juice, grape juice and guava juice is not suggested!