SESSION 2019-2020

Delhi Public School

CHEMISTRY INVESTIGATORY PROJECT

STUDY OF CONSTITUENTS OF ALLOY

SUBMITTED TO

CENTRAL BOARD OF SECONDARY EDUCATION, NEW DELHI

SUPERVISED BY: SUBMITTED BY:

Mrs. Uzma Najam Aditi Kathait

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 Topic

Study of
Constituents of
Alloys
(Bronze and Brass)

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 CERTIFICATE

This is to certify that Aditi Kathait of Class XII-A during the academic year

2019-2020 has successfully completed the Chemistry Project work and

submitted it in this volume to my entire satisfaction in the partial fulfillment

of her certificate of All India Senior Secondary Certificate

Examination(AISSCE) from Central Board of Secondary

Education(CBSE), New Delhi.

Mr. Sudarshan Sonar Mrs. Uzma Najam

(Principal)

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 Acknowledgement
I am highly grateful to my parents and our principal Mr. Sudarshan

Sonar, who helped me by providing all the essential bringing out this

project.

I am very much thankful to Mrs. Uzma Najam who showed me the path

for accomplishing my project work, also for her valuable guidance and

precious suggestions. Every word in this project reflects her challenging

assistance and tremendous command.

I feel highly obliged to be a student of this incomparable institute Delhi

Public School, Moradabad which has been a source of strength,

knowledge, inspiration, and self-esteem for all of us.

Aditi Kathait

XII-B

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 INDEX

S. No: Title Page no:

Certificate 03
1.

Acknowledgement 04
2.

Introduction 06
3.

Experiment 1–Brass 9
4.

Experiment 2-Bronze 12
5.

Conclusion 17
6.

Bibliography 18
7.

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 Introduction

An alloy is a mixture or metallic solid solution composed of two or

more elements. Complete solid solution alloys give single solid phase

microstructure, while partial solutions give two or More phases that may

or may not be homogeneous in distribution, depending on thermal (heat

treatment) history Alloys usually have different properties from those of

the component elements.

The term alloy is used to describe a mixture of atoms in which the primary

constituents is a metal. The primary constituent is a metal. The primary

metal is called the base, the matrix or the solvent. The secondary

constituents are often called solutes. If there is a mixture of only two types

of atoms, not counting impurities, such as a copper-nickel alloy, then it is

called a binary alloy. If there are only three types of atoms then it is called

a ternary alloy. An alloy with four constituents is a quaternary alloy, while

a five-part alloy is termed a quinary alloy.

The percentage of each constituent can be varied with any mixture the

entire range of possible variations are called a system. In this respect, all

of the various forms of an alloy containing only two constituents like iron

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and carbon is called a binary system, while all of the alloy combinations

possible with a ternary alloy, such as alloys of iron, carbon and chromium,

is called a ternary system.

The complete analysis of an alloy involves two steps, qualitative and

quantitative analysis. In qualitative analysis, the components of the alloy

are found out and in quantitative analysis their percentage composition is

determined.

The purpose of this project is to determine qualitatively, the contents

of samples of Brass and Bronze.

Uses of Alloys

i) To modify chemical reactivity:-

a. When sodium is used as reducing agent it is too reactive to be

used but its alloy with mercury, called sodium amalgam can be

safely used as reducing agent. ii) To increase hardness:-

b. Hardness of gold is increased by adding copper to it. Also zinc is

added to copper to make copper hard in form of brass.

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iii) To increase tensile strength:-

c. Nickeloy, an alloy of Nickel (1%), Copper (4%) and aluminium

(95%) has high tensile strength.

iv) To lower the melting point:-

d. Solder metal which is an alloy of Sn(30%) and Pb(70%) has

very less melting point as compared to melting points of Sn

and Pb.

v) To modify the colour:-

e. Aluminium bronze an alloy of Cu and Al has a beautiful golden

colour.

vi) To resist corrosion:-

f. Iron gets rusted and corroded. Its corrosion takes place with

time but for stainless steel, an alloy of iron (98%) and carbon

(2%) does not get rusted.

Experiment 1
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Aim:
To analyse a sample of brass qualitatively.

Requirements:

China dish, test-tube funnel, filter paper and common laboratory reagents.

Theory:

Brass is an alloy of copper and zinc with the following Composition:

Cu = 60-90% and Zn. = 10-40%.

Thus Cu and Zn. form the main constituents of brass. Both these metals

dissolved in 50% of nitric acid due to formation of nitrates which are

soluble.

3Cu + 8HNO3 3Cu (NO3)2 + N2O + 5H2O

4Zn + 10HNO3 4Zn (NO3)2 + N2O + 5H2O

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The solution is boiled to expel the oxides of nitrogen and the resulting

solution is tested for Cu2+ and Zn2+ ions.

Procedure:

1. Place a small piece of brass in a china dish and heat this with

minimum quantity of 50% HNO3 so as to dissolve the piece

completely.

2. Continue heating the solution till a dry solid residue is obtained.

3. Dissolve the solid residue in dil. HCl and filter. Add distilled water to

the filtrate.

4. Pass H2S gas through the filtrate. A black precipitate of copper

sulphide is obtained. Separate the black ppt. and keep the filtrate for

the test of Zn2+ ions Dissolve black ppt. by heating them with 50%

HNO3. To this solution add ammonium hydroxide solution.

Appearance of deep blue colouration in the solution shows the presence

of copper ions in the solution.

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5. To test Zn2+ ions, boil the filtrate to remove H2S gas, then add solid

NH4Cl to this and heat to dissolve NH4Cl. Add excess of NH4OH so

that a solution is ammonical. Now pass H2S gas through this

ammonical solution. Dirty white or grey precipitate indicates zinc.

6. Separate the precipitates and dissolve it in minimum amount of dil.

HCl. Boil to expel H2S gas and add potassium Ferro cyanide solution,

white or bluish white ppt. confirm Zn2+ ions in the solution.

Result:

The given sample of brass contains copper and zinc metals as the main

constituents.

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 Experiment 2

Aim:

To analyze a sample of bronze qualitatively

Requirements:

China dish, test-tube funnel, filter paper and common laboratory reagents.

Theory:

Bronze is an alloy of copper and tin with the following.

Composition:

Cu = 88-96% and Sn. = 4-12%.

Thus copper and zinc form the main constituents of bronze. Both these

metals dissolved in nitric acid.

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Cu + HNO3 Cu2+ + NO + H2O

Sn + HNO3 H2SnO3 + NO2 + H2O

(Conc. acid) (Metastannic Acid)

Excess of nitric acid is removed by heating the solution. The resulting

solution now would contain Cu2+ ions and metastannic acid. This solution

is acidified with dil. HCl and H2S gas is passed when the sulphides of

copper and tin are formed.

Cu2+ + S2 CuS (Black ppt)

H2SnO3 + 2H2S SnS2 (Black ppt.) + 3H2O

The sulphides are separated by boiling the ppt. with yellow ammonium

sulphide when SnS2 goes into solution as

Thiostannate where as CuS is not affected.

SnS2 + (NH4)2S (NH4)2 SnS2 (Soluble)

Ammonium thiostannate. CuS + (NH4)2S

CuS (Unaffected)

Black ppt.

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The soluble black ppt. is tested for Cu2+ ions and the solution is tested for

Sn2+ ions as in elementary qualitative analysis.

Procedure:

1. Take about 1g. of small pieces of bronze in a china dish and add to it

5-10 ml. of dil. HNO3.

2. Heat the contents slowly to dissolve copper and tin completely and then

boil the contents to a paste to remove excess of HNO3. All this is carried

out in cup board.

3. Dissolve this dry mass in distilled water containing HCl (1:1) to get a

clear solution.

4. Transfer the solution in a test tube and pass H2S in excess i.e. till the
precipitation is complete. Filter and reject the filtrate.

5. Take the black ppt. in a test tube and add to it 2-3 ml. of yellow
ammonium sulphide and heat. Filter the contents. Black residue is

tested for Cu2+ ions and filtrate is tested for Sn2+ ions.

6. Analysis of black residue:

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Transfer a little of the black ppt. into a test tube. Add to it 2-3 ml. of 50%.

HNO3 and boil the contents of the tube. A light blue or green sol. indicates

the presence of Cu2+. Divide this sol. into two parts.

(a) To one part add excess of NH4OH a deep blue colouration confirms
the presence of Cu2+ ions.

(b) Acidify the second part with acetic acid and add K4 [Fe (CN) 6] i.e.
potassium ferrocyanide solution. A reddish brown ppt. confirms the

presence of Cu2+ ions.

7. Analysis of filtrate:

Boil the filtrate with 1 ml. of dil. HCl. A yellow ppt. is obtained. Dissolve in

1 ml. conc. HCl. To this solution add 0.5 g. of zinc dust and boil it for 2-3

minutes. Filter and to filtrate add 1-2 ml. of mercuric chloride solution. A

white ppt. turning grey on standing confirms the presence of Sn4+ ions.

Result:

The given sample of bronze contains - Copper and Tin as the main

constituents.

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 Conclusion

In this project, a qualitative analysis of two samples of alloys namely,

Brass and Bronze was carried out to determine their constituents. The

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given sample of bronze contains - Copper and Tin as the main

constituents and the given sample of bronze contains - Copper and Tin as

the main constituents.

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 Bibliography

1. www.google.com
2. www.wikipedia.com
3. NCERT Chemistry Class 12
4. Chemistry Class 12 Candid

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