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KENDRIYA VIDYALYA NO.1, BIKANER INVESTIGATORY PROJECT CHEMISTRY

“STUDY THE EFFECT OF METAL COUPLING ON RUSTING OF IRON”

A PACKAGE SUBMITTED TO C.B.S.E IN PARTIAL FULLFILLMENT OF REQUIREMENT OF A.I.S.S.C.E 2010-2011

UNDER GUIDANCE OF: 	 Submitted by: Mrs. Madhulika Sharma	  Lakshyaveer Singh	   XII B P.G.T. Chemistry

Acknowledgment

I am awfully indebted to my guide and teacher Mrs. Madhulika Sharma, P.G.T Chemistry under whose guidance I was able to perform my project. It was able to perform my project. It was her devoted effort and keen interest which helped in completion of my project.

LAKSHYAVEER SINGH XII B

Certificate This is certified that Lakshyaveer Singh of class XII B has completed his project under my guidance. Her approach to work certified has been sincere and satisfactory.

Session: - 2011-12

Mrs. Madhulika Sharma P.G.T Chemistry Kendriya Vidyalya No.1 Bikaner

Contents 	Aim 	Apparatus and Chemicals used 	Theory 	Procedure 	Observations 	Result 	Bibliography

AIM

Study the effect of metals coupling on rusting of iron.

Apparatus and chemicals used

Apparatus: - 1)	Four test tubes. 2)	Four iron nails. 3)	Beaker. 4)	Glass rod. 5)	Wire gauze. 6)	Sand paper.

Chemicals: - 1)	Gelatin(or agar-agar). 2)	Copper wire. 3)	Zinc and magnesium or strip. 4)	Potassium ferricyanide solution and phenolphthalein indicator.

THEORY The gradual eating away of metal when exposed to air and moisture is known as corrosion. The surface become rough and holes or cavities appear which become deeper. The metal gets covered with its oxide, hydroxide or carbonate. The corrosion of iron is called rusting. Iron gets converted with a red or orange layer when exposed to air and moisture. Rusting is a slow electrochemical process in which iron acts as anode and releases two electrons to become ferrous ion, which reacts with hydroxyl ions present in moisture to become ferrous hydroxide which loses water to become hydrated ferric oxide. Anodic region: - Fe  Fe2+ +  2e- 4Fe2+ +  O2 + (4+2X)H2O   2Fe2o3.xH2O + 8H+

Cathodic region: - 	The electrons released by Iron combines with oxygen and water to produce hydroxyl ions. O2 +  		2H2O     +  4e- 	 		4OH- Oxygen 	 Water                        Hydroxyl ions

PROCEDURE 1)	Rub nails with a sand paper to clean their surfaces. Rub till right shining is obtained. Then wash nails with carbon tetrachloride and dry by heating or with a filter paper. 2)	Wind a clean copper wire around one nail, a clean zinc strip or wire around the second nail and clean magnesium wire around the third nail. Place all these and the fourth nail in two Petri-dishes so that they do not touch each other there is enough gap between them. 3)	Preparation of agar-agar solution:- Heat gently about 3 grams of agar-agar and 100cm3 of distilled water in a beaker until all has dissolved and solution is clear. To this hot solution add 10-15 drops of 0.1M potassium ferricyanide solution and stir it well. 4)	Fill the Petri-dish with hot agar-agar solution so that only the lower half of nails is covered with liquid. Cover the Petri-dish and leave them undisturbly for a day. 5)	On cooling, the liquid sets to gel. Observe the patches around the nails. The nail that gets rusted has two patches around it. One patch is blue in color because of the reaction between the ferrous ions formed, with potassium ferrycyanide to form blue ppt. of potassium ferrycyanide to form blue ppt. of potassium ferro-ferricyanide, KFe[Fe(CN)6]. The other patch around the rusted nail is pink because the hydroxyl ions (OH-) formed turn colourless phenolphthalein pink. 6)	There is no coloured patch around the nail which does not rust.

OBSERVATIONS

S.No. Metal pair	Colour of patch	Rusting Occurred or not 1.	Nail(Iron)	Reddish-Brown	Yes 2.	Iron Zinc	Greenish –Black	Not 3.	Iron copper	Reddish-Brown	Yes 4.	Iron Magnesium	Black	Not

RESULT

Coupling of iron with less reactive metal increases corrosion and with more reactive metal decreases or stops iron corrosion.

The contents of this project have been taken from: - 1.	S.K. KUNDRA lab manual of chemistry. 2.	From internet 3.	From reference book (simplified)