Experiment 2 Colorful Solutions of Iron

o

eg (dx2-y2, dz2)

t2g (dxy, dyz, dxz)

假設的球形場 八面體場游離離子

在八面體場中 d 軌域之相對能量

能

量

orbita

l

energy

Color of Fe3+-complex & Fe2+-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

c

cation: transition metal

anion: ligand

Color Change of Fe2+(aq) 、 Fe3+(aq) ：Fe3+(aq) Fe2+(aq)

A: KSCN(aq) FeSCN2+(aq) ×

B: K4Fe(CN)6(aq) Fe4[Fe(CN)6]3(s) K2Fe[Fe(CN)6](s)

C: K3Fe(CN)6(aq) Fe[Fe(CN)6](aq) Fe4[Fe(CN)6]3(s)

D: BaCl2(aq) FeCl3(aq) FeCl2(aq) + BaSO4(s)

E: tannic acid(aq) Fe3+-tannate(s) Fe2+-tannate(aq)

F: oxalic acid(aq) Fe(C2O4)33(aq) FeC2O4(s)

G: NaOH(aq) Fe(OH)3(s) Fe(OH)2(s)

H: Na2S(aq) FeS(s) FeS(s)

Reduction of Fe3+(aq) by Sn2+(aq) ：Sn2+(aq) + 2Fe3+(aq) Sn4+(aq) + 2Fe2+(aq) ΔE° = 0.632 V

Oxidation of Fe2+(aq) by Ce4+(aq) ：Ce4+(aq) + Fe2+(aq) Ce3+(aq) + Fe3+(aq) ΔE° = 0.929 V

ceric ammonium nitrate ((NH4)2Ce(NO3)6)

tin(II) chloride (SnCl2)

Fe(s) + NaOH(aq) ？

Fe(s) + H2SO4(aq) ？

Another test ： Fe2+(aq) + K3Fe(CN)6(aq) ？

Acid-base reaction of bulk Iron ：

Iron gall ink (Dark blue ink):A purple-black or brown-black ink made from Fe2+

solution and tannic acid.

Ink-bleaching reagent (Ink discoloring solution) Oxalic acid has stronger interaction for binding with Fe2+

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 (K4Fe(CN)6)potassium ferricyanide (K3Fe(CN)6)barium chloride (BaCl2)

tannic acidoxalic acidsodium hydroxide (NaOH)sodium sulfide (Na2S)ferric chloride (FeCl3)tin(II) chloride (SnCl2)sulfuric acid (H2SO4)ceric ammonium nitrate ((NH4)2Ce(NO3)6)ammonium iron(II) sulfate ((NH4)2Fe(SO4)6)

Chemicals：

5.0 mL H2SO4 5.0 mL NaOH

1 drop of 2~3 drops of 10 drops of

Colorful Solutions of Iron

(evenly shake)

(observe)

(observe) (observe

)

1 drop of 2~3 drops of10 drops of

(evenly shake)

(observe)

(observe) (observe

)

ddH2O

(heating to graduation 5)

ddH2O3 drops of dilute H2SO4(aq)

0.6 g of tannic acid

ddH2O3 drops of Arabian gum(aq)

(stir for dissolving)

Iron gall ink (Dark blue ink)(after dry)

ddH2Ooxalic acid

(observe)

10 drops of K3Fe(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 FeCl3(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 SnCl2(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 (NH4)2Fe(SO4)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 (NH4)2Ce(NO3)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 calculatorand the juice without pulp!Suggestion: lemon juice, orange juiceApple juice, grape juice and guava juice is not suggested!