Chemistry Project on Preparation of Potash Alum

Certificate

OF POTASH ALUM

This is to certify that this project work is

submitted by ABCDE to the

Chemistry department, Avbfhd school,

was carried out by him under

the guidance & supervision during academic

year 2014-2015.

Principal Teacher

Mrs. OPUR Mr. MJKL

BMJDKEK (Head of chemistry dept.)

Kovaya

PREPARATIOIN OF POTASH ALUM

ACKNOWLEDGEMENT

I wish to express my deep gratitude and sincere thanks

to Principal, Mrs. ABCED, XYZ school, kovaya for her encouragement and for all the

facilities that she provided for this project work. I

sincerely appreciate this magnanimity by taking me into

her fold for which I shall remain indebted to her.

I extend my hearty thanks to Mr. MKJL ,

chemistry  HOD, who guided me to the successful

completion of this project. I take this opportunity to

express my deep sense of gratitude for his invaluable

guidance, constant encouragement, constructive

comments, sympathetic attitude and immense

motivation, which has sustained my efforts at all

stages of this project work. I am also thankful to Mr.

..(Pkdkdksl).. who has helped in each step of my

project work.

I can’t forget to offer my sincere thanks to my

classmates who helped me to carry out this project

work successfully & for their valuable advice & support,

which I received from them time to time.

ALUM

DECLARATION

I do hereby declare that this project work has

been originally carried under the guidance and

supervision of Mr. MKLKJKK, head of

chemistry department, DFKJSDF school....

ALUM

INTRODUCTION

Aluminium because of its low density, high

tensile strength and resistance to corrosion is widely used

for the manufacture of aeroplanes, automobiles lawn

furniture as well as for aluminium cans. Being good

conductor of electricity it is used for transmission of

electricity. Aluminium is also used for making utensils.

The recycling of aluminium cans and other aluminium

products is a very positive contribution to saving our

natural resources. Most of the recycled aluminium is

melted and recast into other aluminium metal products or

used in the production of various aluminium compounds,

the most common of which are the alums. Alums are

double sulphates having general formula

X2SO4.M2(SO4)3.24H2O

X = Monovalent cation; M = Trivalent cation

Some important alum and their names are given below:

K2SO4.Al2(SO4)3.24H2O - Potash Alum

PREPARATIOIN OF POTASH ALUM

Na2SO4.Al2(SO4)3.24H2O - Soda Alum

K2SO4.Cr2(SO4)3.24H2O - Chrome Alum

(NH)2SO4.Fe2(SO4)3.24H2O - Ferric Alum

Potash alum is used in papermaking, in fire

extinguishers, in food stuffs and in purification of water

soda alum used in baking powders and chrome alum is

used in tanning leather and water proofing fabrics.

In addition to these primary uses, alum is also used as

i. An astringent a substance or preparation that draws

together or constricts body tissues and is effective in

stopping the flow of blood or other secretions. Alum has

also been used by conventional hairdressers for treating

shaving cuts,

ii. A mordant substances used in dyeing to fix certain

dyes on cloth. Either the mordant (if it is colloidal) or a

colloid produced by the mordant adheres to the fiber,

attracting and fixing the colloidal mordant dye. The

insoluble, colored precipitate that is formed is called a

lake. Alum is a basic mordant used for fixing acid dyes.

iii. For the removal of phosphate from natural and

waste waters the aluminium ions of alum combine with

the orthophosphate around pH 6 to form the solid

aluminum hydroxyphosphate which is precipitated and

iv. For fireproofing fabrics The major uses of alums are

based on two important properties, namely precipitation

of Al(OH)3 and those related to the acidity created by the

production of hydrogen ions.

Al(H2O)6

+3 → Al(OH)3 ↓ + 3H2O + 3H+

The H+ ions generated are used foe reacting with sodium

bicarbonate to release CO2. This property is made use of

in baking powder and CO2 fire extinguishers.

AIM

To prepare potash alum from aluminium scrap

REQUIREMENT

 250 ml flask

 Funnel

 Beaker

 Scrap aluminium or cola can

 Potassium hydroxide solution (KOH)

 6 M Sulphuric Acid (H2SO4)

 Water Bath

 Ethanol

THEORY

Aluminum metal is treated with hot aqueous KOH

solution. Aluminium dissolves as potassium aluminate,

KAl(OH)4, salt.

2Al(s) + 2KOH(aq) + 6H2O(l)  2KAl(OH)4 (aq) + 3H2

Potassium aluminate solution on treatment with dil.

Sulphuric acid first gives precipitate Al(OH)3, which

dissolves on addition of small excess of H2SO4 and

heating.

2KOH(aq) + H2SO4(aq)  2Al(OH)3 (s) + K2SO4(aq) + 2H2O(l)

2Al(OH)3 (s) + 3 H2SO4(aq)  Al2(SO4)3(aq) +6H2O(l)

The resulting solution is concentrated to near saturation

and cooled. On cooling crystals of potash alum crystallize

out.

K2SO4(aq) + Al2(SO4)3(aq) + 24H2O(l)  K2SO4.Al2(SO4)3.

24H2O(s)

ALUM

REACTIONS

2Al(s) + 2KOH (aq) + 6H2O (l)  2KAl (OH)4 (aq) + 3H2

K2SO4(aq) + Al2(SO4)3(aq) + 24H2O(l)  K2SO4.Al2(SO4)3.

24H2O(s)

2Al(OH)3 (s) + 3 H2SO4(aq)  Al2(SO4)3(aq) +6H2O(l)

2KOH(aq) + H2SO4(aq)  2Al(OH)3 (s) + K2SO4(aq) + 2H2O(l)

K2SO4(aq) + Al2(SO4)3(aq) + 24H2O(l)  K2SO4.Al2(SO4)3.

24H2O(s)

PROCEDURE

 Clean a small piece of scrap aluminium with steel

wool and cut it into very small pieces. Aluminium foil

may be taken instead of scrap aluminium.

 Put the small pieces of scrap aluminium or

aluminium foil (about 1.00g) into a conical flask and add

about 50 ml of 4 M KOH solution to dissolve the

aluminium.

 The flask may be heated gently in order to facilitate

dissolution. Since during this step hydrogen gas is

evolved this step must be done in a well ventilated area.

 Continue heating until all of the aluminium reacts.

 Filter the solution to remove any insoluble impurities

and reduce the volume to about 25 ml by heating.

 Allow the filtrate to cool. Now add slowly 6 M

H2SO4 until insoluble Al(OH)3 just forms in the solution.

Procedure

 Gently heat the mixture until the Al(OH)3 precipitate

dissolves.

Cool the resulting solution in an ice-bath for about 30 minutes

whereby alum crystals should separate out. For better results the

solution may be left overnight for crystallization to continue.

In case crystals do not form the solution may be further

concentrated and cooled again.

Filter the crystals from the solution using vacuum pump, wash

the crystals with 50/50 ethanol-water mixture.

Continue applying the vacuum until the crystals appear dry.

Determine the mass of alum crystals.

OBSERVATION

Mass of aluminium metal =…………….g

Mass of potash alum =…………….g

Theoretical yield of potash alum =……………g

Percent yield =……………%

RESULT

Potash alum of % yield was prepared from

aluminium scrap.

BIBLIOGRAPHY

 iCBSE.com

 Wikipedia,

 Chemicalland.com

 books.google.co.in