April 14th 2015

EXPERIMENT VIPHOTOCHEMICAL REDUCTION OF ION IRON (III)

A. ObjectivesStudy the iron (III) reduction as a result of photochemical reaction and understand their application in blueprints.

B. Theoritical BasicPhotochemistry is part of chemistry that studies the interaction between atoms, small

molecules and light (or electromagnetic radiation). As with other disciplines, photochemical use SI units or metric system. Units and constants are often used include the meter, second, hertz, joules, moles, R the gas constant, and constants Bolztmann. All units and constants is also part of the field of physical chemistry.

Concentrated nitric acid, cold, iron ions are formed into a passive, in these circumstances, it does not react with dilute nitric acid nor creak copper and a copper salt water solution. (G. Svehla, 1985: 257)

Photochemistry is the study of chemical reactions induced by light directly or indirectly. Ordinary thermal reaction which takes place in the dark obtain the activation energy of the photon absorption of light by molecules. Therefore this reaction gives the possibility high selectivity, which means that the energy of a quantum of light appropriate for a particular reaction. The excited electronic state of the molecule and the energy distribution of electrons having different from the ground state, so that the properties of different kimianyapun. (Alberty, 1984)

Photochemical reaction is a chemical reaction caused by light or ultraviolet radiation. Incoming photon is absorbed by molecules excited reactant molecules or molecules produce free radicals, which then reacts again. (Alberty, 1984)

In photochemical there are two basic laws. According to the first law of Grothus (1817) and Draper (1843), photochemical changes can only be brought about by light absorbed. Radiation is not absorbed but can push the excited molecules to emit light. The second law of photochemical proposed by Stark and Einstein (1908-1912) states that the molecule that absorbs the incoming light quantum becomes activated. (Alberty, 1984)

Photosynthesis is a chemical reaction that requires light to allow the formation of sugars from cellulose may occur from CO2 and H2O. The sunlight helps the formation of vitamin D in the body. Bleaching cloth and straw material usually using sunlight. The blueprint was developed by emitting light on iron compounds. In the world of photography silver and halogen compounds undergo changes by light. (Biddle, 1949)

Blue print processing is still very rare, but the manufacturing process is usually very easy blueprint blueprint paper, coated with iron ammonium citrate and potassium ferisianida are sensitive to light. The imaging process is done on a translucent fabric or paper placed on top of a sheet of blueprint paper and opened the place irradiated by intense light. Light turn iron ammonium citrate salt of a compound of iron, then when the paper soaked in water, salts of iron reacts with potassium ferisianida to form a dark blue solution which makes the paper

becomes blue. Chemicals on paper protected from light by a line of paper or dissolving the image and result in paper or image to white. The blueprint was developed by emitting light on iron compounds. In the world of photography silver and halogen compounds undergo change of the light. (Biddle, 1949)

Absorption of electromagnetic radiation by ionic species in solution requires electrons in the ion can move from one energy level to another. Absorbed light must have energy equal to the difference and the energy levels in transisisi. If the transition energy lies at wavelengths of visible light, then the light component is absorbed and transmitted light will be colored. Transmitted light color is the complementary color and the color is absorbed. The rise of an electron from a low energy level to a higher level of lead absorption components of white light and the light that is passed colors.

Iron is the second metal that abundance in nature after the firt of aluminium. Most of the iron is in the form of hematite, Fe2O3, magnetite, Fe3O4, lemonit, FeO(OH) and siderite, FeCO3. Ferrous metals easily soluble in dilute mineral acids. With non-oxidizing acids and free air, the iron ions will dissolve into the iron (II), whereas if there is aair or oxidizing acids will be produced ions o iron (III).

Ions of iron (III) in solution easily reduced to iron (II) with a weak reducing agent, such as I-ion.

Fe3+ + I- → Fe2+ + ½ I2

Ion solution, ions of iron (III) form complexes with water molecules as a ligand. This complex ion has a tendency to undergo hydrolysis.

2[Fe(H2O)6]3+ → [Fe(H2O)4(OH)2 Fe(H2O)4]4+ + 2H+

[Fe(H2O)6]3+ → [Fe(H2O)5(OH)]2+ + H+

(Team of lectureship inorganic chemistry, 2015)C. Equipment and Material

Equipment :1. 1 piece glass 400 ml beaker2. The dark room (cupboard)3. Chips of glass4. Tweezers

Material :1. 1 M oxalic acid2. 0.1 M diammonium hydrophosphate3. Solution of iron (III) chloride 0.1 M4. HVS paper and tracing paper5. 0.1M hydrochloric acid solution6. Solution of K3Fe(CN)6 0.1M7. Solution of 0.03M K2Cr2O7

8. Filter paper

D. Work Instruction

10 ml of iron (III) chloride 0.5M in 10 ml diammonium hydrophosphate 0.5M mixed

Kept the solution in a dark room

Added 10 ml of oxalic acid 1M, stired in dark room. Closed the

cupboard and opened only when necessary

Taked 4 sheets of HVS paper and dip into the solution in cupboard

The paper removed and olace it between 2 filter paper. Leave paper in between the 2 filter paper for 10-15 minutes until paper dry.

The paper must be dried for one night, the paper was used as a sensitive paper

Object made on tracing paper with black ink/object with black paper

Place the pbject on sensitized paper and nip with two pieces of glass, hited in the sunlight for 4-5 minutes

E. Result of observation1. Color of iron (III) chloride solution at first : orange / yellow brownish2. Color of diammonium hydrophosphate solution first: colorless3. Color of mixed solution : yellow4. Color of the solution plus a mixture of oxalic acid : yellow5. Color of paper after being immersed in the solution : yellow - brownish6. Printouts (result of printing) :

Object Papper Lighting (minutes) NoteWrite ITA Tracing 5 Can’t printoutSign = Carton 10 Object can

printout, but only a half part

Write FRIDA Tracing 15 Can’t printoutSign Carton 20 Object can

printout, but indistinct

7. Reactions :Iron(III) chloride + Diammonium hydrophosphate

FeCl3(aq) + (NH4)2HPO4(aq) → FePO4(aq) + 2NH4Cl(aq) + HCl(aq)

Mixture-1 + oxalic acid

2FePO4(aq) + 3H2C2O4(aq) → 2 FeC2O4(aq) + 2 H3PO4(aq) + 2CO2(g)

Ion reaction :

Reduction : 2Fe3+ + 2e- → 2Fe2+

Oxidaton : C2O42- → 2CO2 + 2e-

Redox : 2Fe3++ C2O42- → 2Fe2+ + 2 CO2

Dip into hexacyanoferrat(III) ion

Fe2+(aq) + [Fe(CN)6]3-

(aq) → Fe3+(aq) + [Fe(CN)6]4-

(aq)

Fe3+(aq) + [Fe(CN)6]4-

(aq) → Fe[Fe(CN)6]

Washed with potassium dichromate

Sensitive paper that has been irradiated with light then dipped into a solution of hexacianoferrat ion (III) 0.1M (ketuker

langkah kerjanya)

Removed paper and dip it in a dilute solution of potassium dichromate 0.03M, washed the paper with 100 ml of HCl,

followed by tap water and let it dry in atmosphere

3K2Cr2O7(aq) + 2 [Fe(CN)6]3-(aq) → 2K3[Fe(CN)6](aq) + 3 Cr2O7

2-(aq)

Washed with HCl

K2Cr2O7(aq) + 2HCl(aq) → 2KCl(aq) + H2Cr2O7(aq)

F. DiscussionPhotochemical reduction of iron (III) experiment is to study that reduction of iron (III)

with sunlight used to aplication blue printout. Iron (III) reducted become iron (II), this

experiment need 2 condition there are nothing light (dark room) and light.

Practicant who has little body go into dark room, then mix iron (III) chloride solution and

diammonium hydrophosphate solution in dark room. Iron (III) chloride solution as oxidator

and contain Fe3+ ion, it’s has orange color. Diammonium hydrophosphate as solution to retard

reduction reaction, it’s has colorless. In this iron(III) still iron (III). Then add oxalic acid

solution for mixture-1. Oxalic acid as reductor, it has colorless. In this part iron (III) reducted

become iron(II). Stirr them and cover the dark room maximally, in order to not any light enter

into dark room. In dark room occurs reaction called antiphotochemical reaction. Look at this

reaction :

Iron(III) chloride + Diammonium hydrophosphate

FeCl3(aq) + (NH4)2HPO4(aq) → FePO4(aq) + 2 NH4Cl(aq) + HCl(aq)

Mixture-1 + oxalic acid

2FePO4(aq) + 3H2C2O4(aq) → 2 FeC2O4(aq) + 2 H3PO4(aq) + 2 CO2(g)

Redox : 2 Fe3++ C2O42- → 2 Fe2+ + 2 CO2

Based on reaction iron (III) already reducted become iron (II). Characteristics also change, the color of mixture solution is yellow.

We make sensitive paper use HVS paper, 4 pieces. We must make also model or object on tracing and carton paper. In tracing paper, made word. In carton paper, made shape and cut it.

When mixture solution adsorb on HVS, dried HVS use filter paper in up and down. Filter paper can adsorb liquid from HVS because has high adsorption capability. Set the sensitive paper like as glass, object paper (tracing paper with word “ITA”), sensitiv papper and glass again. Why must like that? Glass function is cover sensitive paper and object paper from sunlight direct. Object paper in upper than sensitive paper, inorder to sensitive paper touch sunlight. So sensitive paper adsorp color from sun, and choose color which suitable with wave long from mixture solution.

Group 3 make variation of paper kinds, object, and time for lighting. The papers are tracing and carton paper. On tracing paper created word (“ITA” and “FRIDA”), but on carton prepare created shaped (“=” and “ “). Various of lighting time are 5, 10, 15, and 20 (in minutes). For paper with word “ITA” lighted for 5 minutes, paper with shape = lighted for 10

minutes, paper with word “FRIDA” lighted for 15 minutes, and paper with shape lighted for 20 minutes.

Certainly lighting need good light, fortunatelly when practicum the weather is bright. Function of light is remove printout from object paper to sensitive paper. This process called photochemical, there are chemistry reaction using sunlight. Photochemical reaction can change Fe2+ to Fe3+.

Every object papper dipped be spread evenly in potassiumhexacyanoferrat [K3Fe(CN)6]. [K3Fe(CN)6] produce blue color on object papper, so we can look object. After that dipped object paper in potassium dichromate K2Cr2O7. Potassium dichromate solution clean up another substance not any needed. Then dipped it into HCl, HCl solution can clean up another substance which not succesed if only use K2Cr2O7. Look at this reaction :

Fe2+(aq) + [Fe(CN)6]3-

(aq) Fe3+(aq) + [Fe(CN)6]4-

(aq)

Below iron (III) and complex of Fe gather together produce blue solution. Look at this reaction:

4Fe3+(aq) + 3[Fe(CN)6]4-

(aq)               Fe4[Fe(CN)6]3(aq)

Blue trunbull

Based on reaction, sensitive paper can printed blue color if success.

Dip-2 use potassium dichromate solution. The function of potassium dichromate solution

is cleaner another substance needless. Dip-3 use HCl solution, the function of HCl is clean

residue which not bundle by K2Cr2O7. It can also clean diammonium excess. Dip-4 use flow

water from crane, water can remove HCl excess. So printing seen clearly.

Based on experiment, that not occurs for all object paper. For paper with word “ITA”

lighted for 5 minutes, it can’t printout. For paper with shape = lighted for 10 minutes, it can

printout, but only a half part. For paper with word “FRIDA” lighted for 15 minutes, it can’t

printout. The paper with shape lighted for 20 minutes, it printout but indistinct. Based on

theory, time lighting influence printout. As long time as, blue printout more clearly. But group

3, only carton paper which printout. But that still not enough perfect. It means occurs mistaken

from experiment. Maybe that occurs because :

a) Solution (FeCl3, diammonium hydrophosphate, and oxalic acid) already little

contaminated because touch light when mixed. Dark room not really dark room,

because there still a space.

b) Solution (FeCl3, diammonium hydrophosphate, and oxalic acid) not adsorb

maximally by HVS papper, because dipping not along 15 minutes but less from that.

c) Drying not enough, after diped into mixture solution (FeCl3, diammonium

hydrophosphate, and oxalic acid).

G. Conclusion1. Reduction reaction iron (III) can use light, it’s called photochemical reaction.

2. In this experiment, we need 2 condition there are bright and dark.

3. If increasingly time of lighting, so increase too ion Fe(III) reducted and blue printout

more clearly.

4. Based on experiment there are mistaken cause printout not perfect.

H. Suggestion1. We must keep dark room from light.2. The sensitive paper must dried actually after diped into mixture solution (FeCl3,

diammonium hydrophosphate, and oxalic acid).

I. Refference

Alberty, R.A. 1984. Thermodinamic of Biochemical Reaction. New Jersy: John Wiley and Sons Inc.

Biddle,H.C. 1949. Chemistry Today”. USA: Rand Mcalley and Company.Inorganic Chemistry Lecturer Team. 2015. Manual Work of Inorganic Chemistry Practicum.

Semarang : UNNES.Svehla, G. 1990. Vogel Buku Teks Analisis Anorganik Kualitatif Makro dan Semimikro.

B agian 1 dan 2 Edisi kelima. Jakarta: PT. Kalman Media Pustaka.