chemistry project ali

7/28/2019 Chemistry Project Ali

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LORD MAHAVIRA SCHOOL

INVESTIGATORY PROJECT

OF

CHEMISTRY

Session : 2012-2013

SUBMITTED BY: SUBMITTED TO:WAZAHAT ALI SANGEETA SHARMA


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TABLE OF CONTENTSCertificate

Acknowledgement

Introduction

Electrochemical Mechanism(rusting)

Method of preventing of Corrosion

Aim of the project

Material required

Procedure

Observation table

Result

Conclusion

Bibliography


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This is to certify thatWAZAHAT ALIStudent of class XII, LORD MAHAVIRA SCHOOL hascompleted the project titledTO STUDY THE EFFECTOFMETAL COUPLING ON THE RATE OF CORROSION.During the academic year (2012-2013) toward partial

fulfillment of credit for the CHEMISTRY.Practical evaluation of AISSCE-2013. And submitted

satisfactory report, as compiled in the following pages

under my supervision.

Teachers Signature.....


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ACKNOWLEDGEMENTIt would be my pleasure to express my sincere

thanks to My Chemistry Teacher Mrs.SANGEETA SHARMA in providing a helping handin this project. Her unflagging patience, creativity

and immense knowledge that she shared with me

have proved highly beneficial to me and have

made my Project File both possible and successful.

I would also like to thanks our principal Mrs.SUNAINA and all my friends who were directly orindirectly involved in this project.

WAZAHAT ALI


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INTRODUCTIONMetals and alloys undergo rusting andcorrosion.The process by which someMetals when exposed to atmosphericconditions i.e.,moist air, carbondioxideform undesirable compounds on thesurface is known as Corrosion. Thecompounds formed are usuallyoxides.Rusting is also a type of corrosion but

the term is restricted to iron orproductsmade from it. Iron is easily prone torusting making its surface rough.Chemically, rust is a hydrated ferric

oxide Fe2O3.nH2O. Rusting may beexplained by an electrochemicalmechanism.


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Electro chemicalMechanism(rusting)

In the presence of moist aircontaining dissolved oxygen or carbondioxide, the commercial iron behaves asif composed of small electrical cells.At

anode of cell, iron passes in to solutionas ferrous ions.

Fe Fe2+ +2e

The electrons from the above reaction

move towards the cathode and formhydroxyl ions

H2O+ (O) + 2e 2OH

Under the influence of dissolved oxygen

the ferrous ions and hydroxyl ionsinteract from rust, i.e., hydrated ferricoxide.

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


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2Fe3+ + 6OH Fe2O3.3H2O (rust) or

2Fe(OH)3

If supply of oxygen is limited theCorrosion product may be black

Anhydrous magnetite, Fe3O4 .


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Method of preventiNGof CorrosioN

Some of the methods used to preventcorrosion are discussed here :

1.Barrier Protect ion . In this method, a

barrier film is introduced between ironsurface and atmospheric air.The film isobtained by painting , varnishing etc.

2.Galvanization. The metallic iron isn

covered by a layer of more active metalsuch as zinc.The active metal loseselectrons in preference to iron

Zn Zn2++ 2e

Thus, protecting iron from rusting andCorrosion.


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Aim of the project

The goal of the project is toinvestigate

effect of metal coupling on the rateof rusting of iron.


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Material required Beakers-15

Iron sheets of size-6

Aluminium rods of size-6

Brass rods of size-6 Zinc sheets of size-6

Measuring cylinders

Chemical Balance

Weight box

CHEMICALS:

Hydrochloric acid

Sodium hydroxide.


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EXPERIMENTAL

PROCEDURE

(i) Mix 9 ml. of conc. HCl with 241 ml. of water to

form 250 ml. of solution.

(ii) Take this solution in seven different beakers.

(iii) Mark each beaker serially from 1 to 7.

(iv) Take the weights of three iron sheets, threealuminium rods, three brass rods and three zincsheets.

(v) Now keep iron sheets, aluminium rods, zincsheets and brass rod in separate beakers.


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(vi) Then take iron + brass, iron + aluminium,iron + zinc, aluminium + zinc and brass + zincand keep them in different beakers.

(vii) Allow the reactions to occur for 24 hours.

(viii) Note the maximum and minimum

temperatures.

(ix) Now at the end of reaction take out themetals and keep them in sun for sometime sothat they get dried up quickly

(x) Take the weights of each specimen and notethe difference.

(xi) Similarly repeat 1,2,3,4,5,6,7 and 8 steps in abasic solution.


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Observation tableS.No. Specimen (with

acid) Initial Weight(in gm) Final Weight(in gm)1. Brass 8 5

2. Iron 8 6

3. Zinc 8 6.50

4. Aluminium 8 7.10

5. Iron+Aluminium 15 12.30

6. Brass+Zinc 15 13.00

7. Iron+Zinc 15 14.10S.no Specimen (with

bases)Initial Weight(in gm)

Final Weight(in gm)

8.Brass 8 5.80

9. Iron 8 6.20

10. Zinc 8 7.10

11. Aluminium 8 7.60

12. Iron+Aluminium 15 12.90

13.Brass+Zinc 15 13.60

14. Iron+Zinc 15 14.40


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Result1. The rate of corrosion observed in acidicmedium or the mass consumed during thecorrosion is in the decreasing order from brassto aluminum. Brass has the highest corrosion

rate while aluminium has the least corrosionrate.

Brass > Iron > Zinc > Aluminium.

2. When coupling of these metals was done eachcouple showed some difference in theircorrosion with respect to each metal kept alone.Iron + Aluminium couple has the highest rate ofcorrosion while iron +Zinc couple has the lowestrate of corrosion. Rate of corrosion of each

couple is in the order ofIron + Aluminium > Brass + Zinc> Iron + Zinc.


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3. Rate of corrosion in basic medium is in thedecreasing order from Brass to Aluminium.Theorder of rate of corrosion is as below:

Brass > Zinc >Iron > Aluminium.

4. When these metals were coupled the rate ofcorrosion was in the decreasing order from

Brass+ Aluminium > Brass + Zinc > Iron +Aluminium.

5. Temperature and time of reaction wereconstant i.e., temperature was 21 C and time of

reaction was 24 hours.


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CONCLUSION Corrosion is a serious problem of somemetals like iron, zinc, aluminium and alloyslike brass which are commonly used in dayto day life.

Apart from reducing the life of articles madeup of these metals or alloys the chemicalsubstances formed out of corrosion haveserious public health problems.

Replacement of machines or their parts andmany other articles in industrial and publicdealing lead to huge expenditure.

Hence, how to reduce or avoid corrosion ofarticles made up of metals or alloys has beena major subject of study in the field ofchemistry and electro-chemistry.


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The study of the rate of corrosion of differentmetals or alloys showed gradualdecrease in their masses in acidic medium.The decrease is in the order of brass,iron,zinc, aluminium.

The present experiments are in fullagreement with the well known electro-chemical reaction. Some of the typicalreactions as occur with iron are illustrated.

(a) The reactions at respective electrodesare:

At cathode:Fe . Fe2+ + 2e.

in acid the equilibrium isHCl H+ + Cl.

At anode: The water which is in equilibrium

H2O H+ + OH.


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Here the Fe2+ cation will readily take Cl and formFeCl3. While H

+ of acid wil lbe reacting withanother H+ of water and will form H2 gas. WhileOH. anion will also react with some of the ironand will form Fe(OH)3 which is observed in theform of rust.

(b) The e.m.f of these metals are in the order

of Al:Zn:Fe . The values are e.m.f

Al Al3++3e- 1.66V

Zn Zn2++2e- 0.76V

Fe Fe2++ 2e- 0.44V

Brass which is an alloy of zinc and copperhas the e.m.f. 0.42V during the forwardreaction or oxidation reaction. While inbackward reaction the e.m.f. value is .0.42.This is because during oxidation reaction thee.m.f values of zinc and copper are .0.76 and


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+ 0.34, respectively. That is why the valuediffers.

(c) In acid there are replaceable H+ ionswhich react with metals and H2 gas isevolved. This is because all the metals arehighly electronegative in nature. When thesetwo come in contact they react very easily

and form stable compounds. Thus the rate ofcorrosion is very high.The rate of corrosionin basic medium is very less as compared toacidic medium. This is shown because offollowing factors:

(i) Ex: sodium hydroxide .NaOH which is in

equilibrium with Na+ and OH. ions.

NaOH . Na+ + OH- When NaOH comes incontact with water the two ions immediatelydissociate. The hydrates Na+ ions will take

the H+ ion.The electropositive charactershere will be the main factor in the slow rateof corrosion.Na being more electropositivethan the metal mentioned above, most of OH-


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ions will be taken by Na+ when compared tothe other metals i.e., the rate of corrosion isslow with

Na+ \ Fe2+ || OH\OH-

While H+ + electron = HH + H = H2 gas.

(ii) The availability of e- is very less for theconversion of H+ to H2 gas state. That is whythere will not be replaceable H ion. If there

is no replaceable H+ ion then the corrosionwill be possible. Hence the rate of corrosion

is very slow.


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BIBLIOGRAPHYFor our project we have taken help from

following sources.

1) Comprehensive (Practical Chemistry

XII)

2) Internet- www.wikipedia.com,

www.encylopedia.com

3) NCERT Chemistry Textbooks

4) PRADEEP chemistry textbooks for

11th and 12th
http://www.encylopedia.com/http://www.encylopedia.com/

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