Investigatory Project Chemistry Class 12 4571m

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INVESTIGATORY PROJECT ON

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“Metal coupling on rusting of iron”

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Submitted by Ajay Panwar

Roll no :Std (XIIth)

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CERTIFICATE

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This is to certify that Ajay panwar has 17successfully completed the investigatory 18project titled “Metal coupling on rusting of 19iron” and submitted to the Dept. of Physics 20,Montfort secondary school, Nagpur and carried 21out by him under the guidance and supervision 22of Ms. Savita Ajay during the academic session 232014-2015. The said work has been assessed 24and found to be up to the standard envisaged 25for the level of course. 16

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DATE:-

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Rev.Bro.Jagan Mohan

Reddy 32(Physics teacher) 31

(Principal)

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INDEX

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Sr.no

1. 2.   3. 4. 5. 6. 7. 8. 9. 10.

CONTENTS

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ACKNOWLEDGEMENT INTRODUCTION Rusting on electrochemical mechanism Methods to prevent corrosion OBJECTIVE MATERIAL REQUIRED DIAGRAM PROCEDURE OBSERVATION RESULT PRECAUTION

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BIBLIOGRAPHY

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ACKNOWLEDGEMENT

Primarily I would thank God for being able to 41complete this project with success. Then I 40

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would like to express my sincere gratitude to 43my physics teacher Mrs. for her 44vital ,guidance and encouragement 45without which this project would not have come 46forth, and lab assistance and 47throughout the project. I would like to thank my 48friends who have helped me with their valuable 49suggestions and guidance has been helpful in 50various phases of the completion of the project. 51Last but not the least I would like to thank my 52classmates who have helped me a lot.. 42

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-AJAY PANWAR

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Roll No:STD 12th

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INTRODUCTION

Metals and Alloys undergo rusting and 62corrosion. The process by which some metals 63when exposed to atmospheric condition i.e., 64moist air, carbon dioxide from undesirable 65compounds on the surface is known as 66corrosion. The compounds formed are usually 67oxides. Rusting is also a type of corrosion but 61

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the term is restricted to iron or products made 69from it. Iron is easily prone to rusting making 70its surface rough. Chemically, rust is a hydrated 71ferric oxide Fe2O3.nH2O . 68

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Rusting an Electrochemical Mechanism-

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Rusting may be explained by an electrochemical 79mechanism. In the presence of moist air 80containing dissolved oxygen or carbon dioxide, 81the commercial iron behave as if composed of 82small electric cells. At anode of cell, iron es 83into solution as ferrous ions. 84 Fe Fe 2+ + 2e85The electron moves towards the cathode and 86form hydroxyl ions. 87 H2O + (O) + 2e2OH88Under the influence of dissolved oxygen the 89ferrous ions and hydroxyl ions interact to form 90rust i.e. hydrated ferric oxide. 78

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2Fe2+ + H2O + (O) 2Fe3+ +6OH -

2Fe3+ + 2OHFe2O3.3H2O (Rust)

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Methods of prevention of corrosion and rusting

Some of the methods used to prevent corrosion 103and rusting are discussed below:102

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 Barrier protection: - In this method, a barrier film is introduced between iron surface and atmospheric air. The film is obtained by painting varnishing etc.

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 Galvanization: - the metallic iron is

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covered by a layer of more reactive metal such as zinc. The active metal losses electrons in preference of iron. Thus, protecting from rusting and corrosion. Zn Zn2+ + 2e-

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Objective :

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Materials required: -

Two petridishes, four iron nails, beaker, sand 134paper, wire gauge. Gelatin, copper, zinc and 135magnesium strips, potassium ferricyanide 136solution, phenolphthalein. 133

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Diagram:-

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Procedure:-

1. Clean the surface of iron nails with the help of 153 sand paper. Wash them with carbon tetrachloride 154 and dry on filter paper. 1552. Wind a clean strip around one nail, a clean copper 156 wire around the second and clean magnesium strip 152

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around the third nail. Put all these three and a 158 fourth nail in petridish so that they are not in 159 with each other. 1603. Preparation of agar agar solution. Heat about 3g 161 of agar agar in 100ml of water taken in a beaker 162 until solution becomes clear. Add about 1ml of 0.1M 163 potassium ferri-cyanide solution, 1ml of phenol164 phthalein solution and stir well the contents. 1654. Fill petridishes with hot agar agar solution in 166 such a way that only lower half of nails are covered 167 with liquid. 1685. Keep the covered petridishes undisturbed for one 169 day or so. 1706. The liquid sets to gel on cooling. Two types of 171 patches are observed around the rusted nail, one is 172 blue and the other pink. Blue patch is due to the 173 reaction between Ferrous ions and potassium 174 ferricyanide to form potassium Ferro- ferricyanide, 175 KFe[Fe(CN)6] whereas pink patch is due to the 176 formation of hydroxyl ions which turns colorless 177 phenolphthalein to pink. 157

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Observation:-

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S.No

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Metal pair

Colour of patch

Nail rusts or not

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1. Iron-zinc

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Ironmagnesium Iron-copper

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Iron-nail

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Conclusion: -

It is clear from the observations that coupling 183of iron with more electropositive metal such as 184zinc and magnesium resists corrosion and 185rusting of iron. Coupling of iron with less 186electropositive metal such as copper increases 187rusting. 182

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BIBLIOGRAPHY

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THE GIVEN SOURCE OF INFORMATION IS TAKEN 198FROM 197

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 Comprehensive (Practical Chemistry XIIth)  Internet ,www.google.com th  NCERT Chemistry textbook (XII )

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