VELAMMAL VIDYALAYA

ANNEXURE

CHEMISTRY PROJECT

ACADEMIC YEAR: 2024 – 2025

TOPIC: FINDING REFRACTIVE INDICES

PREPARED BY

NAME :Dharan Karthick.R

CLASS & SEC :12-IIT

DATE OF SUBMISSION :

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 ACKNOWLEDGEMENT

In the accomplishment of this project successfully, many people have bestowed their
blessings and heart pledged support up on me, I take this opportunity to express my
gratitude to all, who have been instrumental in the successful completion of this project.

Primarily, I express my deep sense of gratitude to the luminary, The Principal, Dean and
SR.HM for providing the best of facilities and environment to bring out innovation and
spirit of inquiry through this venture.

I am deeply indebted to my teacher , without whose

constructive feedback, this project would not have been successful. The valuable advice and
suggestions for correction, modifications and improvement did enhance the quality of the
task.

I would also like to thank my parents, friends and all the members who contributed to this
project was vital for the success of the project.

I am grateful for their constant support and help.

VELAMMAL VIDYALAYA

ANNEXURE

NAME : BATCH NO :

CLASS : REGD.NO. :

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 CERTIFICATE

Certified that this is a bonafide Record of Practical work done by

Mr. / Miss. in

the Laboratory during the year 2024.

Teacher-In-Charge

Submitted for the Practical Examination in

at held on

INTERNAL EXAMINERS EXTERNAL EXAMINERS

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 STERILIZATION
OF WATER
USING BLEACHING
POWDER
CHEMISTRY INVESTIGATORY PROJECT
[This project gives an outlook of the technique “STERILIZATION
OF WATER USING BLEACHING POWER” which is used to
purify water and makes it fit for drinking.]

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 INDEX

 Introduction
 Water Purification
 History of Water Purification
 Sterilization of Water
 Experiment
 Bibilograph

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INTRODUCTION
Water:

Water, a substance composed of the chemical elements hydrogen and oxygen and existing in
gaseous, liquid, and solid states. It is one of the most plentiful and essential of compounds. A
tasteless and odourless liquid at room temperature, it has the important ability to dissolve many
other substances. Indeed, the versatility of water as a solvent is essential to living organisms.

Life is believed to have originated in the aqueous solutions of the world’s oceans, and living
organisms depend on aqueous solutions, such as blood and digestive juices, for biological
processes. In small quantities water appears colourless, but water actually has an intrinsic blue
colour caused by slight absorption of light at red wavelengths.

Although the molecules of water are simple in structure (H 2O), the physical and chemical
properties of the compound are extraordinarily complicated, and they are not typical of most
substances found on Earth.

Water is an important and essential ingredient in our quest for survival on this planet. It is very
essential for carrying out various metabolic processes in our body and also to carry out
Hemoglobin throughout the body

Now a day’s demand of drinking water is increased dramatically due to increase in world
population. As many water resources are not suitable for drinking, they need to be

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processed/purified. The water either contains excess Calcium or Magnesium salts or any other
organic impurity, which makes the water not fit for drinking.

Water Purification
There are many methods for purification of water. Some of them are listed:

1. Boiling
2. Filtration
3. Bleaching Powder Treatment
4. SODIS (Solar Water Disinfection)

Boiling:
Boiling is the most commonly used method for purifying water. It is a mainly used in households
and an efficient method too. But when it comes to large scale it is not suitable because in small
quantities the loss of water due to evaporation is very less. But in large scale especially
industries, the water will be boiled in large amount so that the loss of water due to evaporation is
high and the amount of purified water would be less obtained.

Filtration:
Filtration is used for separating or removing foreign impurities or foreign solute. Reverse
Osmosis is mainly used in filtration method. But the major drawback of this method is removing
of foreign chemicals or impurities that are miscible in water.

SODIS:
SODIS or Solar Water Disinfection is a simple water treatment technology that can be used in
household level. In this method water is filled in a clean bottle and exposed in strong sunlight for
around 6 hours. The process is made even more safe and effective if the bottom half of the bottle
or the surface it's lying on is blackened, and/or the flat surface is made of plastic or metal. It's the
combination of heat and ultraviolet light which kills the organisms.

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The drawback of this method is this method depends on the climate and the time consumed for
purification process is more. Small quantities of water can be treated and does not treat with
chemical pollution

THEORY
History of Water Purification:
In 1854 it was discovered that a cholera epidemic spread through water. The outbreak seemed
less severe in areas where sand filters were installed. British scientist John Snow found that the
direct cause of the outbreak was water pump contamination by sewage water. He applied
chlorine to purify the water, and this paved the way for water disinfection. Since the water in the
pump had tasted and smelled normal, the conclusion was finally drawn that good taste and smell
alone do not guarantee safe drinking water. This discovery led to governments starting to install
municipal water filters (sand filters and chlorination), and hence the first government regulation
of public water.

In the 1890s America started building large sand filters to protect public health. These turned out
to be a success. Instead of slow sand filtration, rapid sand filtration was now applied. Filter
capacity was improved by cleaning it with powerful jet steam. Subsequently, Dr. Fuller found
that rapid sand filtration worked much better when it was preceded by coagulation and
sedimentation techniques. Meanwhile, such waterborne illnesses as cholera and typhoid became
less and less common as water chlorination won terrain throughout the world.

But the victory obtained by the invention of chlorination did not last long. After some time the
negative effects of this element were discovered. Chlorine vaporizes much faster than water, and
it was linked to the aggravation and cause of respiratory disease. Water experts started looking
for alternative water disinfectants. In 1902 calcium hypo chlorite and ferric chloride were mixed
in a drinking water supply in Belgium, resulting in both coagulation and disinfection.

The treatment and distribution of water for safe use is one of the greatest achievements of the
twentieth century. Before cities began routinely treating drinking water with chlorine (starting
with Chicago and Jersey City in US in 1908), cholera, typhoid fever, dysentery and hepatitis A
killed thousands of U.S. residents annually. Drinking water chlorination and filtration have
helped to virtually eliminate these diseases in the U.S. and other developed countries. Meeting
the goal of clean, safe drinking water requires a multi-barrier approach that includes: protecting
source water from contamination, appropriately treating raw water, and ensuring safe distribution
of treated water to consumers’ taps. During the treatment process, chlorine is added to drinking
water as elemental chlorine (chlorine gas), sodium hypochlorite solution or dry calcium
hypochlorite. When applied to water, each of these forms “free chlorine,” which destroys
pathogenic (disease-causing) organisms. Almost all systems that disinfect their water use some
type of chlorine-based process, either alone or in combination with other disinfectants. In

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addition to controlling disease-causing organisms, chlorination offers a number of benefits
including:

• Reduces many disagreeable tastes and odors;

• Eliminates slime bacteria, molds and algae that commonly grow in water supply reservoirs, on
the walls of water mains and in storage tanks;

• Removes chemical compounds that have unpleasant tastes and hinder disinfection; and

• Helps remove iron and manganese from raw water. As importantly, only chlorine-based
chemicals provide “residual disinfectant” levels that prevent microbial re-growth and help
protect treated water throughout the distribution system.

For more than a century, the safety of drinking water supplies has been greatly improved by the
addition of bleaching powder. Disinfecting our drinking water ensures it is free of the
microorganisms that can cause serious and life-threatening diseases, such as cholera and typhoid
fever. To this day, bleaching powder remains the most commonly used drinking water
disinfectant, and the disinfectant for which we have the most scientific information. Bleaching
powder is added as part of the drinking water treatment process. However, bleaching powder also
reacts with the organic matter, naturally present in water, such as decaying leaves. This chemical
reaction forms a group of chemicals known as disinfection by-products. Current scientific data
shows that the benefits of bleaching our drinking water (less disease) are much greater than any
health risks from THMs and other by-products. Although other disinfectants are available,
bleaching powder remains the choice of water treatment experts.

When used with modern water filtration methods, chlorine is effective against virtually all
microorganisms. Bleaching powder is easy to apply and small amounts of the chemical remain in
the water as it travels in the distribution system from the treatment plant to the consumer’s tap,
this level of effectiveness ensures that microorganisms cannot recontaminate the water after it
leaves the treatment.

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 STERILIZATION OF WATER USING BLEACHING POWDER

Bleaching Powder:
The chemical name of bleaching powder is Calcium hypochlorite with chemical formula
Ca(OCl2). Bleaching powder is a pale yellowish powder existing with a strong smell of chlorine.
It is soluble in water but due to the presence of impurities, we never observe a clear solution.

Uses of Bleaching Powder:

• It is used as a disinfectant which is used for disinfecting water to make potable water.  It
is used for bleaching dirty clothes in the laundry and as a bleaching agent for cotton and
linen in the textile industry.
• It is a strong oxidizing agent, hence used as an oxidizer in many industries.

Preparation of Bleaching Powder:

It is prepared by the action of chlorine on dry slaked lime.

CaOH2+Cl2 CaOCl2 +H2O

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Why is Bleaching Powder used for sterilization?
Bleaching powder is used as a disinfectant for water supply because it releases chlorine, which
kills many pathogens.

How is Water sterilized using Bleaching Powder?

This chemical can be used for sterilizing water by Using 5 drops of bleach per each half gallon of
water to be purified, and allowing it to sit undisturbed for half an hour to make it safe for
drinking. Letting it sit several hours more will help reduce the chlorine taste, as the chlorine will
slowly evaporate out. A different reference advises when using household bleach for purification;
add a single drop of bleach per quart of water which is visibly clear, or three drops per quart of
water where the water is NOT visibly clear. Then allow the water to sit undisturbed for half an
hour.

Processes involved in disinfecting and purifying water:

The combination of following processes is used for municipal drinking water treatment
worldwide:

1. Pre-chlorination - for algae control and arresting any biological growth

2. Aeration - along with pre-chlorination for removal of dissolved iron and manganese

3. Coagulation - for flocculation

4. Coagulant aids also known as polyelectrolyte’s - to improve coagulation and for thicker floc
formation

5. Sedimentation - for solids separation, that is, removal of suspended solids trapped in the floc

6. Filtration - for removal of carried over floc

7. Disinfection - for killing bacteria

Out of these processes, the role of Bleaching powder is only in the last step i.e. for Disinfection
of water.

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 EXPERIMENT

Aim: To determine the dosage of bleaching powder required for sterilization or disinfection of
different samples of water.

Requirements:
Burette, titration flask, 100ml graduated cylinder, 250ml measuring flask, weight box, glazed tile,
glass wool. Bleaching Powder, Glass wool, 0.1 N Na2S2O3 solution, 10% KI solution, different
samples of water, starch solution.

Pre-Requisite Knowledge:
1. A known mass of the given sample of bleaching powder is dissolved in water to prepare a
solution of known concentration. This solution contains dissolved chlorine, liberated by
the action of bleaching powder with water.

CaOCl2+H20 Ca(OH)2+Cl2

2. The amount of Chlorine present in the above solution is determined by treating a known
volume of the above solution with excess of 10% potassium iodide solution, when
equivalent amount of Iodine is liberated. The Iodine, thus liberated is then estimated by
titrating it against a standard solution of Sodium thiosulphate, using starch solution as
indicator.
Cl2+2KI 2KCl+I2
I2+2Na2S2O3 Na2S4O6+2NaI

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 3. A known Volume of one of the given samples of water is treated with a known volume of
bleaching powder solution. The amount of residual chlorine is determined by adding
excess potassium iodide solution and then titrating against standard sodium thiosulphate
solution.

4. From the readings in 2 and 3, the amount of chlorine and hence bleaching powder
required for the disinfection of a given volume of the given sample of water can be
calculated.

Procedure:
1. Preparation of bleaching powder solution. Weigh accurately 2.5g of the given sample of
bleaching powder and transfer it to a 250ml conical flask. Add about 100-150ml of distilled
water. Stopper the flask and shake it vigorously. The suspension thus obtained is filtered
through glass wool and the filtrate is diluted with water (in a measuring flask) to make the
volume 250ml. The solution obtained is 1% bleaching powder solution.

2. Take 20ml of bleaching powder solution in a stoppered conical flask and add it to 20ml of
10% KI solution. Stopper the flask and shake it vigorously. Titrate this solution against 0.1N
Na2S2O3 solution taken in the burette. When the solution in the conical flask becomes light
yellow in color, add about 2ml starch solution. The solution now becomes blue in color.
Continue titrating till the blue color just disappears. Repeat the titration to get a set of three
concordant readings.

3. Take 100ml of the water sample in a 250ml stoppered conical flask and add it to 10ml of
bleaching powder solution. Then add 20ml of KI solution and stopper the flask. Shake
vigorously and titrate against 0.1N Na 2S2O3 solution using starch solution as indicator as
described in step 2.

4. Repeat the step 3 with other samples of water and record the observations.

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 BIBILOGRAPH
https://www.britannica.com/science/water

https://sswm.info/sswm-solutions-bop-markets

https://byjus.com/

https://www.doubtnut.com/

https://www.netsolwater.com/

http://www.cbseportal.com

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