TOPIC : Effect of metal coupling on the rusting of iron

b.c. PUBLIC SCHOOL2016-2017

SUBMITED TO:- MRS. anju MAM

SUBMITED BY:-BHARATa ram CHOUDHARY

certificate

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This is to certify that Bharata Ram Choudhary, a student of class XII science has successfully completed the research project on the topic “Effect of metal coupling on rusting of iron” under the guidance of Mrs. ANJU SHARMA (Subject Teacher).

This project is absolutely genuine and does not indulge in plagiarism of any kind.The references taken in making this project have been declared at the end of this report.

Signature Signature (Subject Teacher). (Principal

Mam)

ACKNOWLEDGE

I feel proud to present my Investigatory project in Chemistry on the topic “Effect of metal coupling on rusting of iron”.This project wouldn’t have been feasible without the proper and rigorous guidance of my Chemistry teacher Mrs. Anju Sharma who guided me throughout this project in every possible way. An investigatory project involves various difficult lab experiments which have to be carried out by the student to obtain the observations and conclude the report on a meaningful note. These experiments are very critical and in the case of failure, may result in disastrous consequences. Thereby, I would like to thank mam for guiding me on a step by step basis and ensuring that I completed all my experiments with ease.Rigorous hard work has been put in this project to ensure that it proves to be the best. I hope that this project will prove to be a breeding ground for the next generation of students and will guide them in every possible way.

BHARAT CHOUDHARY

ACKNOWLEDGE

CONTENTS

1. Introduction

2. Objective of project

3. Aim

4. Requirements

5. Theory

6. Procedure

7. Observation

8. Result

9. Bibliography

10. Remarks

CONTENTS

INTRODUCTION

Metals and alloys undergo rusting and corrosion. The process by which some metals when exposed to atmospheric condition i.e., moist air, carbon dioxide form undesirable compounds on the surface is known as corrosion. The compounds formed are usually oxides. Rusting is also a type of corrosion but the term is restricted to iron or products made from it .Iron is easily prone to rusting making its surface rough. Chemically, rust is a hydrated ferric oxide Fe2O3.nH2O.Rusting may be explained by an electrochemical mechanism. In the presence of moist air containing dissolved oxygen or carbon dioxide, the commercial iron behave as if composed of small electrical cells. At anode of cell, iron passes into solution as ferrous ions.

Fe → Fe2+ + 2 e−

The electrons from the above reaction move towards the cathode and form hydroxyl ions

H2O + (O) + 2 e−→ 2OH-

Under the influence of dissolved oxygen the ferrous ions and hydroxyl ions interact to form rust, i.e., hydrated ferric oxide. 2Fe2+ + 2 H2O + (O) +2e-→2Fe3+ + 2OH-

INTRODUCTION

2Fe3+ + 6OH- → Fe2O3.3H2O or 2Fe(OH)3

(RUST)If we supply of oxygen is limited the corrosion product may be black anhydrous magnetite,Fe3O4.Methods of Prevention of Corrosion and Rusting1. Barrier protection : In this method a barrier is placed between metal and atmosphere. This is actually done by coating the metals surface with paint oil or grease. The barrier avoids the direct contact of the metal surface with the environment and hence prevents corrosion.2. Galvanization : In this method the iron object is covered with a thin coating of metal like zinc which is more reactive than iron. Here the active metal which is coated will act as anode and undergo oxidation in preference to iron. The process of coating iron objects with zinc is called galvanization.

Zn → Zn2+ + 2e-

Objective of project

In this project the aim is to investigate effect of the metals coupling on the rusting of iron. Metal coupling affects the rusting of iron . If the nail is coupled with a more electro-positive metal like zinc, magnesium or aluminium rusting is prevented but if on the other hand , it is coupled with less electro – positive metals like copper , the rusting is facilitated.

AIM

To study the effect of metal coupling on rusting of iron.

AIM

REQUIREMEN

1) Two Petri dishes2) Four test – tube3) Four iron nails4) Beaker5) Sand paper6) Wire gauge7) Gelatin8) Copper, zinc & magnesium strips9) Potassium ferricyanide solution10) Phenolphthalein

REQUIREMEN

THEORY

• Corrosion is a serious problem of some metals like iron, zinc, aluminium and alloys like brass which are commonly used in day to day life.

• Apart from reducing the life of articles made up of these metals or alloys the chemical substances formed out of corrosion have serious public health problems.

• Replacement of machines or their parts and many other articles in industrial and public dealing lead to huge expenditure.

• Hence, how to reduce or avoid corrosion of articles made up of metals or alloys has been a major subject of study in the field of chemistry and electro-chemistry.

THEORY

PROCEDURE

1)At first we have to clean the surface of iron nails with the help of sand paper.

2) After that we have to wind zinc strip around one nail, a clean copper wire around the second & clean magnesium strip around the third nail. Then to put all these three and a fourth nail in Petri dishes so that they are not in contact with each other.

3) Then to fill the Petri dishes with hot agar solution in such a way that only lower half of the nails are covered with the liquids .Covered Petri dishes for one day or so.

4) The liquids set to a gel on cooling. Two types of patches are observed around the rusted nail, one is blue and the other pink. Blue patch is due to the formation of potassium ferro-ferricyanide, KFe[Fe(CN)6] where pink patch is due to the formation of hydroxyl ions which turns colourless phenolphthalein to pink.

PROCEDURE

BIBLIOGRAPHY

This all information taken from :-1. Practical book of chemistry2. www.google.com3. www.wikipedia.com4. NCERT chemistry textbook

BIBLIOGRAPHY

REMARKS

OBSERVATION

S.No. Metal Pair Colour of the patch

Nails rusts or not

1 Iron- Zinc Blue No2 Iron -Magnesium Blue No3 Iron- Copper Pink Yes4 Iron – Nail Pink Yes

CONCLUSION

It is clear from the observation that coupling of iron with more electropositive metals such as zinc and magnesium resists corrosion and rusting of iron. Coupling of iron with less electropositive metals such as copper increases rusting.

RESULT

Two types of patches are observed around the rusted nail

1. One is blue- due to the formation of potassium Ferro-ferricyanide

2. Pink patch is due to the formation of hydroxyl ions which turns colorless phenolphthalein to pink

It is clear from the observation that coupling of iron with more electropositive metals such as zinc and magnesium resists corrosion and rusting of iron. Coupling of iron with less electropositive metals such as copper increases rusting.