Estimation of Chlorides in any water body ( Pond water)

Estimation of Chlorides in any water body( Pond water)

1. [TYPE THE COMPANY NAME]
Estimation of Chlorides
in any water body
( Pond water)


Submitted By: Sadia Rahat (15)
MS

2. 1



Table of Contents
GRAVMETRIC ANALYSIS ......................................................................................................................2
TYPES OF GRAVIMETRIC TECHNIQUES..................................................................................................2
CHLORIDES .........................................................................................................................................2
PERMISSIBLE LIMITS OF CHLORIDE IN DIFFERENT WATER BODIES..........................................................3
EQUIPMENTS NEEDED ........................................................................................................................3
METHOD ............................................................................................................................................4
PROCEDURE .......................................................................................................................................4
OBSERVATION AND CALCULATION.......................................................................................................5
Result ................................................................................................................................................7
Thus, there are about 0.297% of chlorides present in our pond water sample. .......................................7
PRECAUTIONS ....................................................................................................................................7
ENVIRONMENTAL SIGNIFICANCE .........................................................................................................7
ENVIRONMENTAL IMPACTS.................................................................................................................8
REFERENCE ........................................................................................................................................8

3. 2
GRAVMETRIC ANALYSIS
It is the quantitative determination of an analyte based on the mass of a solid. In this
technique we usually use an excess of added reagent reacts with the analyte to form a
precipitate. The precipitate is filtered, dried, and weighed. Its mass is used to calculate the
concentration of the analyte in the given sample.
TYPES OF GRAVIMETRIC TECHNIQUES
Gravimetry is one of only a small number of definitive techniques whose measurements
require only base SI units, such as mass or the mole, and defined constants, such as Avogadro’s
number and the mass of
12
C. There are usually four types of gravimetric techniques.
 Electro-gravimetric technique
 Volatilization gravimetric technique
 Precipitation gravimetric technique
In our particular problem, we are going to use precipitation Gravimetric technique. In
precipitation gravimetry an insoluble compound forms when we add a precipitating reagent, or
precipitant, to a solution containing our analyte. In most methods the precipitate is the product
of a simple metathesis reaction between the analyte and the precipitant; however, any reaction
generating a precipitate can potentially serve as a gravimetric method (Summerfield and Reid,
2010).
Range of analytes can be detected and estimated through gravimetric techniques such as
SO4 can be analyzed through barium chloride, Cl
-
etc.
PROBLEM: ESTIMATE THE AMOUNT OF CHLORIDES IN THE GIVEN WATER BODY (POND
WATER) SAMPLE.
We use gravimetric technique to determine the chloride ion concentration of pond
water solution by gravimetric analysis. A precipitate of silver chloride is formed by adding a
solution of silver nitrate to the aqueous solution of chloride ions. The precipitate is collected by
careful filtration and weighed.
Ag
+
+ Cl
–
→ AgCl(s)
CHLORIDES
Earth crust usually contains about 0.05% of chlorides in it. Chlorides are present in
almost every kind of waterbody such as ground water, canal water, aquifers etc. Normal
concentration of chlorides in fresh water body is about 1-100ppm. However sea water usually
contains 35,000ppm chlorides.

4. 3
Some of the plants and microorganisms are adapted to live in brackish (mixed fresh and
salt) water. but once chlorides entered in water body it is really difficult to remove them
thoroughly, even water treatment plants are not able to remove them hundred percent. The excess
of salt in water bodies may threaten the biological integrity of aquatic ecosystems (Robertson et
al., 1938).
PERMISSIBLE LIMITS OF CHLORIDE IN DIFFERENT WATER BODIES

National environmental Quality Standard for municipal and industrial effluents in Pakistan
Sr. No Parameter mg/L
1 Chloride (Cl
-
) Existing Standard 1000
2 Chloride (Cl
-
) Into Wetland Waters 1000
3 Chloride (Cl
-
) Into Sewage Treatment 1000
NEQS, 2008
Standards for Quality Drinking Water in Pakistan
Sr. No. Parameter mg/L
1 Standard values of Chloride (Cl
-
) for Pakistan <250
2 Standard values of Chloride (Cl
-
) according
to WHO guideline
250
3 Standard values of Chloride (Cl
-
) according
to USA guideline
250
WHO, 2003
EQUIPMENTS NEEDED
 Analytical Balance
 pipettes
 250 mL conical flask
 Bunsen burner
 Measuring cylinders
 Whatman filter paper 41
 Filtering Flask
 Stirrer

5. 4
METHOD
SAMPLE PREPARATION
We filtered sample water to remove all kind of impurities that were present in the form
of sand or grit particles. We filter 20 ml sample water.
REAGENTS PREPARATION
0.1 M Silver Nitrate (AgNO3) in 150ml Distilled Water
We carefully weigh 2.54grams of silver nitrate through analytical balance. Dissolve it in
150 ml distilled water. This is our 0.1 molar solution of AgNO3.
1M solution means mass of one mole of AgNO3 is dissolved in 1000ml of Solution. So,
Molar mass of AgNO3 = 107.8682 + 14 +48 = 169.8682g/mole
1M solution of AgNO3 contains=169.8682 g of AgNO3/1000ml of solution
0.1M solution of AgNO3 contains = 169.8682 × 0.1=16.9868 g of AgNO3/1000ml of
solution
But, here the volume of solution is restricted to 150ml so we will adjust the mass of AgNO3
according to this.
0.1 M solution in 1000ml require the mass of AgNO3= 16.9868g
So, 1ml require the mass of AgNO3 =16.9868/1000ml
And 150ml require the mass of AgNO3=16.9868g/1000ml ×150ml
=2.54g of AgNO3/150ml of solution

We carefully weigh 2.54grams of silver nitrate through analytical balance. Dissolve it in
100 ml distilled water. Mixed well with the help of stirrer and made the final volume upto
150ml. This is our 0.1 molar solution of AgNO3.
PROCEDURE
First of all, we carefully washed all the apparatus with distilled water. Then we carefully
weigh the mass of filter paper by using analytical balance. It is about 1.07 grams. Then we take
4.5 ml AgNO3 by using pipette and add it into 20 ml sample water. During the addition of AgNO3
we continuously shake sample water, so that precipitates could form properly. Then we add 5
ml AgNO3 by using pipette and add it in sample water. We add 5ml more AgNO3 by using
pipette and add it in sample water. Then we filter our sample to collect precipitates formed.
The same process is repeated on the filtrate until we reach a level where no precipitates
are formed on addition of silver nitrate. This represents that all the chloride ions in the solution
have been precipitated out. Then we collect the precipitates formed on previously collected
filter paper.

6. 5
To check if any other chloride present in our water body, we again add 10 ml AgNO3 by
using pipette and add it in sample water. No precipitate form this time. Then we dried up filter
paper and weigh it. This is the mass of filter paper plus precipitates. We subtract the mass of
filter paper from this mass. This is the mass of chlorides precipitates.











OBSERVATION AND CALCULATION
Sr.No Sample
Volume
(ml)
Weight of dry filter
paper(g)
A
Weight of dry filter paper
+ precipitates (g)
B
Weight of
precipitates
C=B-A
1. 20 1.07 1.31 0.24
2. 20 1.07 1.30 0.23
3. 20 1.07 1.32 0.25
Average weight of filter paper+ precipitates=1.31g

7. 6
Weight of filter paper =1.07g
Weight of filter paper and precipitates = 1.31g
Weight of precipitates = 1.31g-1.07g= 0.24g/20ml of sample
Ag
+
+ Cl
–
→ AgCl(s)
The above mentioned equation shows that one mole of Ag reacts with one mole of Cl. It
means that one mole of AgCl contains one mole of silver (Ag) as well as one mole of
chloride (Cl).


Atomic mass of Silver (Ag) =107.8682g
Atomic weight of Chlorine (Cl) = 35.5 g
Grams of AgCl in sample = Weight of precipitates =0.24g

Molecular/Molar mass of Silver Chloride (AgCl) = 107.8682g + 35.5g =143.3982g/mole
Moles of Chloride = Moles of AgCl = Grams of AgCl(S)
Molar mass of AgCl
“So we can write as”

Moles of Chloride = Grams of AgCl(S)
Molar Mass of AgCl
By putting the values

Moles of Chloride = 0.24g = 0.0016737 moles of Cl/20ml of sample
143.3982g/mole
To get the grams of Cl we will use the following formula
Moles of Cl = Grams of Cl
Molar Mass of Cl
Grams of Cl=Moles of Cl × Molar Mass of Cl
Grams of Cl= 0.0016737× 35.5= 0.0594g Cl/20ml of sample
%age of Cl in sample =
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8. 7
=
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= 0.297 % of chloride present in pond water sample
a) Changing g to mg
0.059 * 1000 = 59 mg/20 ml

b) 20 ml of sample (pond water) contain Cl
-
ion = 59 mg
1 ml of sample contain Cl
-
ion = 59/20
1000 ml of sample contain Cl
-
ion = 59/20 * 1000
= 2,950 mg/L or 2,950 ppm

Result
Thus, there are about 0.297% of chlorides present in our pondwater sample.Concentration of
chlorides in our water sample is 2950 ppm. This is higher than the permissible limits which are 250 ppm
in drinking water according to WHO standards. The permissible limit of chlorides in municipal wetland
water is about 1000ppm, so the concentration of chlorides in our water sample is higher than both of
the standards limit.
PRECAUTIONS
We have stored silver nitrates in a bottles cover with brown paper so that it cannot
expose to sun light. We carefully handle the silver nitrate; otherwise it may cause skin irritation
and leave its scars on skin. We have washed our whole apparatus to the distilled water to
remove impurities.
ENVIRONMENTAL SIGNIFICANCE
Chloride implies salty taste in water bodies. So in the areas where the water resources
are scarce, water bodies which contain more than 2000ppm sodium chloride concentration
used as domestic source of salts (Hunt et al., 2012).
Another significant aspect of chloride is that it is use for the chlorination of drinking
water, as it acts as anti-septic and kills harm full bacteria.Appropriate quantity of chlorides is
too much essential for human body. Low concentration of sodium chloride affects the human
endocrinal system (Hunt et al., 2012).

9. 8
ENVIRONMENTAL IMPACTS
The anthropogenic increase in chlorides concentration in different waterbodies causes
many environmental impacts. It threatens the biological integrity of aquatic ecosystems. There
are a variety of sources, causes increase in concentration of chlorides in aquatic water bodies
(Hunt et al., 2012).
Chlorides used as road salts for the purpose of deicing caused abrupt increase in
chlorides concentration in water bodies. Chlorides use as an active ingredient in the form of
sodium chloride or potassium chloride, and when snow beings to melt in summers; the spikes
in roadside streams causes increase in concentration of chloride in drain water (Hunt et al.,
2012).
Chlorides normally use in the form of sodium chloride, in water softeners. These water
softeners causes increased salt concentration in septic systems. Chlorides also have the ability
of corrosions, if present in excessive quantity. Industrial boilers negatively affected by salts
depositions and their life time decreases as well (Hunt et al., 2012).
REFERENCE
 Robertson, J.D. and Webb, D.A. (Nov, 1938). The Micro Estimation of Sodium, Potassium,
Calcium, Magnesium, Chloride and Sulphate in Sea Water and The body Fluids of Marine
Animals. Department of Zoology. Pg. 155-172
 World Health Organization. (2003). Chloride in Drinking Water: WHO Guidelines for Drinking
Water-Quality 2(2).
 Hunt, M., Herron, E. and Green, L. (March, 2012). Chlorides in Fresh Water. The University
of Rhode Island.
 Summerfield, S. Reid, H. (April, 2010). Introduction to Analytical Chemistry.
 Dil, S.A., Qazi, I.A., Baig, M.A., Khan, E.A. and Tahir, A. (June, 2008). National Standards for
Drinking Water Quality. Government of Pakistan. Pakistan Environmental Protection
Agency.
 Environmental Fact Sheet. WD-DWGB. (2010). Sodium and Chloride in Drinking Water. New
Hemisphere.03301