Chemistry Project to Study the Constituents of an Alloy

Study of Constituents of an Alloy

Acknowledgement

I, Souradip Sen of class XII-C express my gratitude to my school authorities for allowing me to undertake the project titled Alloy Analysis. I naturally could not have done justice to my delicate assignment, had I not been privileged to get the animate guidance from Mr. T.N. Dey, Chemistry teacher of Deepika E.M. School.

I also express sincere thanks to my family who extended helping hand in completing this project.

Souradip Sen

Student Internal Examiner External Examiner

Introduction

An alloy is a homogeneous mixture of two or more metals or a metal and non-metal.

They are generally harder than their components with reduced malleability and ductility. Alloys are prepared to enhance certain characteristics of the constituent metals, as per requirement.

In this project, we shall qualitatively analyze the chemical composition of two alloys: Brass and Bronze.

Aim of the Experiment

General Objective

This project is being carried out with a view to increase the appreciation of alloy-analysis as an important branch of chemistry. The hands-on laboratory experience gained is highly beneficial in understanding the general procedure of qualitative analysis of an unknown sample.

Specific Objective

In this project, we shall be analyzing the constituents of Brass and Bronze.

Materials Required

1. Brass and Bronze pieces
2. China dishes
3. Filtration apparatus
4. Nitric acid
5. Hydrogen sulphide gas
6. Ammonium chloride
7. Potassium ferrocyanide
8. Ammonium sulphide
9. Dil. hydrochloric acid

Theory

Brass

Brass contains Cu and Zn. Both dissolve in nitric acid.

4Zn + 10HNO₃ = 4Zn(NO₃)₂ + N₂O + 5H₂O

3Cu + 8HNO₃ = 3Cu(NO₃)₂ + 4H₂O + 2NO

Further analysis is carried out for respective ions.

Cu dissolves in H₂S to give black ppt. of CuS. It is filtered to get the soln. of Zinc Sulphide. It precipitates out in the form of ZnCl₂ in an ammoniacal soln. of Ammonium chloride. The precipitate is dissolved in dilute HCl and then treated with Potassium ferrocyanide to get a bluish-white ppt. of Zn₂[Fe(CN)₆].

Bronze

Bronze contains Cu and Sn. Their nitrates are obtained by dissolving the sample in conc. Nitric acid. The nitrates are precipitated as sulphides by passing H₂S through their solution in dil. HCl.

The CuS is insoluble in yellow ammonium sulphide, while SnS is soluble. The ppt. is separated by filtration.

The ppt. is dissolved in conc. HNO₃ and then Ammonium hydroxide solution is passed through it. Blue colouration confirms the presence of Cu.

The filtrate is treated with conc. HCl followed by Zinc dust to obtain SnCl₂. Then HgCl₂ solution is added. Formation of slate-coloured ppt. indicates the presence of Sn.

SnS₂ + HCl (conc.) = SnCl₄ + H₂S

SnCl₄ + Fe = SnCl₂ + FeCl₂

SnCl₂ + HgCl₂ = Hg₂Cl₂ + SnCl₄

Detail of Procedure and Observations

Brass

1. A small piece of brass was placed in a china dish and dissolved in minimum quantity of 50% conc. HNO₃.
2. The soln. was heated to obtain a dry residue. The residue was dissolved in dilute HCl.
3. H₂S gas was passed and a black ppt. was observed. The soln. was filtered and the ppt. was dissolved in NH₄OH soln. A blue coloration observed indicates the presence of Cu.
4. The filtrate was tested for presence of Zn. Ammonium hydroxide and chloride solutions were added and then H₂S gas was passed. A dull grey ppt. was separated and dissolved in dil. HCl followed by addition of Potassium ferrocyanide. A bluish-white ppt. confirms the presence of Zn.

Bronze

1. The sample was dissolved in 50% HNO₃ and then heated to obtain nitrates.
2. The nitrates were dissolved in dil. HCl and then precipitated as sulphides by passing H₂S gas.
3. The precipitates were treated with yellow ammonium sulphide, when a part of it dissolves. The soln. was filtered.
4. The ppt. was tested for Cu as in the case of brass.
5. The filtrate was treated with conc. HCl followed by Fe dust.
6. Then HgCl₂ soln. was added. Formation of a slate-coloured ppt. confirmed the presence of Sn.

Conclusion

Brass contains Copper and Zinc.

Bronze contains Copper and Tin.

Bibliography

1. Comprehensive Practical Chemistry - Class 12.
2. Inorganic Chemistry.
3. www.niton.com
4. www.alloyanalyzer.nit.edu

Signatures

Student Internal Examiner External Examiner