Water is
the commonest substance on the earth, which covers about 70% of the planet. All
living organisms consist mostly water. Earth, air, fire and water were
considered by some ancient philosophers to be four chemical substances, a
concept that progresses through the middle age. Water is a colourless, clear
liquid usually with boiling (100°C / 212°F) and freezing point (0°C / 3 2°F).
These discrepancies result from the strong attraction that each water molecules
has for others, so that the energy required to meet the solid and boil the
liquid is greater than could be predicted. Water also shows unusual volume
change with increasing temperature. As warm water cools, it contracts until its
reach it maximum density at 4°C (39°F). Further cooling effects on expansion of
the liquid phase, and another expansion occurs when the liquid freezes to form
ice. Both of these peculiarities occur because of the formation of highly
ordered arrangements of hydrogen bonding of the water molecules. Pure water is
a poor conductor, but the impurities found in natural water helps it in its
dielectric constant and as a universal solvent. According to the comments by
Wood Ward 1966), “some water are indeed so very clear and transpired that would
not easily suspect any terrestrial matter were latent in them, but these may be
of highly saturated with such matter.
1. 1 Types of Water
Natural Water:
water includes rain water, lake water and sea water. Rain water is the purest
form of natural water because it is formed as a result of the condensation of
water vapour in the atmosphere, that is, it is a natural form of distilled
water. Spring water contains a considerable amount of mineral salts but very
little suspended impurities such as dust and bacteria. So it is a good source
of drinking water. Well water contains a lot of clay and other minerals salts.
Axell that is used as a source of drinking water should be:
Sited away from sources of underground water pollution
such as pit latrines.
Lined with bricks and covered. Water from deep wells;
tend to be less polluted than that from surface well. Generally it is safer to
boil well water before drinking. River water, lake water and sea water contain
a lot of dissolved air, mineral salts, bacteria and organic remains.
Treated Water:
water is usually prepared for special purposes. Examples of treated water are
distilled water, pipe borne water, and chlorinated water for use in swimming
water is obtained from the treatment of the impure or the natural water in some
forms, it depending on the types of impurities present and the purpose to which
the water is needed for use.
Distilled Water:
This is the
purest of all form of water. It is obtainable in the laboratory where it is
commonly used for the dissolution of substance when undertaking quantitative
analysis. Distilled water is obtained from the condensation of water vapour or
stream through the process called DISTILATION. Thus, distilled water is free of
all solute substances. It is suitable for use in all purpose, but does not give
much pleasure when taken as drinking water due to its tastelessness.
Pipe-borne Water:
This is
another form of treated water and it prepared by filtration and treatment of
the natural or the impure water with chemicals to coagulate solid impurities
and to kill the bacteria and all forms of germs in it. However, pipe- borne
water contains some mineral solute such as Sodium chloride, which are highly
essential to the body. Thus pipe-borne water is the most suitable form of water
for all sorts of domestic purpose, since it is free from germs and disease
vectors that could transmit ailments into human body.
Chlorinated Water:
water is treated with chlorine or other germicides primarily to kill germs of
infection diseases such as diseases of the skin, tuberculosis, liver fluke etc.
which might have been introduced into it by carrier of such diseases.
1.2 Characteristics of Water
The true
picture of the nature of a particular sample of water can be gained by measuring
several different properties through analysis under the broad headings of
physical and chemical characteristics.
Physical Characteristics
properties are in many cases relatively easy to measure and some may be readily
observable by a lay man.
(i) Taste
and Odour: Pure water is tasteless, but this is hardly obtainable in nature
because of the dissolved impurities of ten organic in nature e.g. phenol and
chlorophenol. They are subjective properties, which are difficult to measure.
(ii) Colour:
Pure water is colourless, natural yellow colour in water from upland cantonment
is due to organic acids which not in any way harmful, being similar to tranic
acid from tea.
Turbidity: Water that is not turbid is hardly got In nature. The presence of
colloidal solids e.g. clay, slit, particles and micro-organisms give liquid a
cloudy appearance which is aesthetically unattractive and may be harmful.
Electric Conductivity: The conductivity of a solution depends on the quantity
of dissolved salts present. Other physical properties, which may sometimes be
important, are:
Density (g/dm3) at 4°C.
(viii) High
dielectric constant
Melting point of 0°C.
(x) Neutral
to litmus papers.
Chemical Properties
The chemical
characteristics of water are:
(i) pH: The
intensity of acidity and alkalinity of sample is measured on the pH scale which
actually measures the concentration of hydrogen ions present. Water is weakly
chemical reactions, (H20
à H+ 0H) are
controlled by pH and biological activity is usually restricted to a fairly
narrow pH range of 6 — 8. Highly acidic or highly alkaline waters are
undesirable because of corrosion hazards and possible difficulties in
Oxidation — Reduction Potential (ORP): In any system undergoing oxidation,
there is a continual change in the ratio between the materials in the form and
those in the oxidized form.
Alkalinity: Due to the presence of HCO3, CO3 or OH, most
of the natural alkalinity in water is due to bicarbonate (HCO3) produced by the
action of ground water in limestone or chalk in the presence of carbon dioxide
CaCO3 + H20
+ CO2
à  Ca(HCO3)2
The amount
of alkalinity present is expressed in terms of CaCO3.
Acidity: Most of the natural acidity in water is due to the presence of CO2.
Acidity is also express in terms of CaCO3.
Hardness: This is the property of water which prevents lather formation with
soap and produces scale in hot water system. It is due mainly to the metallic
ion Ca2 and Mg2. There is no health hazard but economic disadvantages of hard
water include increased soap consumption and higher fuel costs. Hardness is
expressed in term of CaCO3 as well.
Dissolved Gases: Gases such as chlorine, oxygen, nitrogen and carbon dioxide
from the atmosphere dissolved in water, and the most important of them all in
water quality control is oxygen.
Hardness of Water
Hard water
will not form lather readily with soap. It contains a number of dissolved salt,
the most important being Calcium tetra-oxosuiphate (VI), Magnessium
tetra-oxosuiphate (VI) and Calcium hydrogen trioxocarbonate (IV). Soap is the
Sodium or Potassium salt of an organic acid (Fatty acid), ordinary soap is
usually sodium octadecanoated origin of hard water. Water acquired hardness
when it dissolves gypsum, (CaCO4.2H20) or limestone (CaCO3) from soil over
which it flows. Gypsum is sparing soluble in water which contains carbon (IV)
oxides, is capable of dissolving small quantities of limestone. The reaction is
as follows:
CaCO3 +
C02(g) + H20 Ca(HCO3)2(aq)
occurs abundantly in nature as water vapour in the atmosphere, as
water or ice in the ocean and in land waters, as water of hydration in many rocks
and minerals in the earth crust.
1 Natural
The purest
form of natural water is rain water, in country districts rain water contains
in solution oxygen, Nitrogen and carbon dioxide absorbed from the atmosphere
and Ammonium nitrate formed by electrical discharges during thunder storms.
Rain water failing over towns is liable to contain also oxides of sulphur
formed from the burning of sulphur, ferrous coal, as well as soil and dust
Rain water
falls on the ground and percolates through the soil, dissolving rocks soluble
in pure water, and those chemically attached by a dilute solution of carbon
The nature
of impurities in spring well or river water must therefore depend on the nature
of the rocks with which the water has been in control, this water frequently
contain the chlorides, sulphates, bicarbonates and carbonates of sodium,
calcium, magnesium and iron, salt of potassium are present less frequently
because they are preferentially retained by the soil.
has shown that lakes are the sources of most impure water with almost 3.6% of
solid matters, and sometimes too, it might be higher. The same research has
equally shown that the most pure or least impure form of water is the rain
water from the country districts.
It contains
about 0.0005% of solid impurity. The earth surface has been
to be 70% water rich and 30% water free.
relative amount of water in circulation in the world is fairly constant.
However, it is sometimes in another use for instance when in circulation. This
circulation of water tends to form gigantic water cycle and it is permanent
operation. The largest collections of natural water are in the seas, lakes,
rivers and oceans. These are directly exposed to the atmosphere and allow
evaporation to take place.
This is the
movement of water molecules into the atmosphere; it is a physical process and
can occur at any temperature under ordinary conditions, evaporation takes place
always and especially on dry sunny day. The water apour that gives into the
atmosphere gets condensed. The condensed water vapour becomes water droplets
floats in the air as cloud messes and the accumulated water falls as rain drop.
Also the rain drops are equally prone to evaporation as soon as it reaches the
earth surface. Therefore, the process of rain dropping is a continuous one,
even though it has been indicated that not all the raindrops are evaporated,
while some are evaporated, some goes down into the soil for plants consumption
and some gather up bigger into the soil they are subject to being found in the
wells. The process behind in this case takes place down beneath the soil. Some
will be absorbed by plants which are equally posted to the air through the
stomata and lenticels. But those which are consumed by the ammals are released
in sweats during excretion or excreted as unne.
hardness of water depends on many factors even though the source of
depends on some factors. An example where a river bed is of impervious
materials like granite, the water may be fairly pure. But in limestone areas,
the river tends to be more harder because the dissolved calcium hydrogen
trioxocarbonate (IV) which is contained in it. Also, it is not good for human
consumption unless it is been treated with chemical unlike the river water, tap
water contains less impurities and it has been already subject to chemical
treatment which makes it more consumable. Apart from the natural causes of hard
water, these are also some consequential causes e.g. streams could be polluted
by organic waster in the cities farms, industries and firms. The water waste in
the cities fanns, industries and firms. Human being can easily contract some
infections, diseases by consuming dirty water, such as dysentery, typhoid, and
cholera, if it is not treated with chemical. The importance of water as a
solution cannot be down-looked. The air we breathe and the water we drink are
solutions. The food we eat is firstly digested and then dissolved in the blood
before transport to other various parts of the body; it is used to produce
energy. Carbon dioxide in the air is dissolved in water in the leaves of green
plants; it will be used to produce oxygen and build tissues. Oxygen which
dissolved in water is always used by the aquatic organism for respiration.
Carbon dioxide is produced and the carbon dioxide produced will dissolve in
water and it is used by water plants to produce oxygen through respiration.
The rain
dissolves gaseous impurities from the atmosphere and will help freshen the air
we breathe. The quality of the water substances dissolved from the rock,
through which underground water and run off from feed and seriously fertilized
farm land pollutes air, river, with hundred of dissolved substances that must
be removed, without proper understanding of the properties of solution we
cannot understand these and related environmental problem.
Electrical Conductivity
in a
completed electric circuit, where water is the electrolyte, the lamp glows,
therefore electricity is being conducted from one electrode to the other
through the solution. A solution that can conduct electricity is called
electrolytes. Infact therefore, solution that do not conduct electricity are
termed non- electrolytes. Tap water is a good electrolyte and some one must be
careful when handling electrical equipment in its presence. However, water is a
weak electrolytes, a weak electrolyte do not dissociate completely when in
example, H20 > H + 01-F, in weak electrolyte, one do realizes that there
would still be hydrogen ion on both element dissociating. To buttress this is the
dissociation of ethanoic acid, CH3COOH > CH300 + W, this is a weak
2.4 Sources
of Water
following are the natural forms and occurrences of water in earth’s
(i) River water
(II) Rain
(iii) Well
(iv) Lakes
and seas (oceans)
(v) Spring
Water: Rivers are formed naturally when spring or similar running water come
together and eventually flows along the same rate. It contains dissolved
particles as well as mineral particles. The minerals particles depend so much
on the river bed.
Where the
river bed for instance is of impervious large, the impurities dissolved will be
fair, but if the river bed is limestone, the water will be hard water. This is
because Calcium hydrogen trioxo-carbonate (IV), Ca(HCO3)2 will be dissolved, so
also bacteria into the river water. Hence, it is very much unsuitable for
drinking otherwise treated with chemicals or boiled.
Rain Water:
Rain water is the purest form of natural water. This is because it is formed as
a result of evaporation and consequent of the water droplets. Hence, this is a
believed to have been naturally distilled. It contain about 0.0005% when
collected in the country districts. However, because it is water, and of course
water is a universal solvent, one may not deny that it can dissolve some gases
in air. To buttress this is the fact that it dissolved nitrogen, Carbon (IV)
oxide, oxygen, dust, air born bacteria but still depends on conditions. It is
usually soft and hence lathers easily with soap.
Well Water:
This is a man-made source of water. The water is under the surface. Hole are
dug to approach the water length of each well depends on the nature and type of
the earth at the particular points. Hence a function whether the place is rocky
or water logged. Well is a stagnant one and may contain remains of the dead
organisms over the ages of long decades.
usually contains clay and therefore not recommended for man consumption unless
treated with alum or boiled.
Lakes and
Seas: These are from reservoirs, river and running water. They are the
reservoirs into which all the impurities eventually go and hence, the solid
content of the sea water is usually high about (3.6°/o impurities). The solids
which are found in the natural water are mainly the suiphates and bicarbonates
hydrogen carbonates) of calcium magnesium together, with smallest amount of
sodium chloride, silicate, nitrate, ammonium salts as well as the gaseous
impurities already mentioned are present in rain water. i.e. Oxygen (02),
Nitrogen (N2) and Carbon (IV) oxide (C02).
percentage of solid matter here is usually veiy high due to the calcium
sulphate and calcium bicarbonate (hydrogen carbonate). Generally the impurities
which maybe present in water may be grouped into classes.
(i) Matter
in solution
(ii) Matter
in suspension.
Each of
these classes may be sub-divided into (a) inorganic or (b)
matter consists of bacteria sewage and other forms of animal and
mater in various stages of decay. There are also some micro-organism found in
natural water. Water which seep through the ground or runs off as surface water
into streams becomes exposed to many kinds of decaying organic matter and
micro-organism, such micro-organisms include algae, fungi, harmless bacteria
and diseases germs, all these may contaminate the water, some of these may
discolour the water and impacting an unpleasant taste or colour. Streams become
polluted from the organic waste materials of cities and farms, such surface
water may become contaminated by water seeping into it. Typhoid and
paratyphoid, dysentery, cholera and other intestinal diseases may result from
the consumption of such water if is not purified (lyons and Carnalan, 1952).
Spring Water:
When it rains, some of the water enters into the porous layer by percolation,
until it collects above the impervious layer. Excess of this water may emerge
again on the soil surface as spring water. During its percolation through the
various layers, it dissolves on a considerable amount of minerals water.
water of course contains solid impurities and suspended impurities in it such
as dust and bacteria and they may be filtered off, spring water is therefore a
good source of drinking water.
2.5 importance
of Water
The aqueous
origin in life justifies the essentiality of water as life’s primary source.
Water is an essential source of life in that; it constitutes a reasonable
percentage of the content of plants and animal cells (between 60% and 800/o).
Plants and
animal depend largely upon water for their daily survival. Water plays vital
roles in the body cells of plant and animal. It is required as a solvent for
biological reactions and for transporting substance across the membranes of
plants and animal body cells, maintaining body temperature, producing digestive
fluid and dissolving waste products for excretion. Inadequate availability of
water to plants leads to a resultant wilting and eventual death of plants.
In man,
insufficient water in the body due to dehydration or otherwise may results to
severe diarrhea, vomiting, fever or unusually high body temperature which may
be very chronic in children, It is however imperative to note that too much of
water intake could also cause a disease called EDEMA which is often observed in
children suffering from kwashiorkor.
we use water for many purposes. We use water for drinking and laundry purpose
such as: drinking, cooking our foods, washing our cloths and utensils and for
bathing, pure water is free from germs and diseases in order to enhance a
perfect healthy life existence.
water is found useful in hospitals in preserved forms which drive into the body
cells of sick patient to ameliorate the death of the amount of water in the cells.
Also water has been found useful as drug to cure many ailments such as fever,
tuberculosis and many others. It was prescribed intervals is capable of curing
any of this body ailment (LUTH).
Water is
highly useful in some firms and industries where drying machines are use. An
example of such firms or industries is the wood industries, where water is
strongly heated in the boiling section to supply steam to drying their
semi-finished and finished products. Water because of its solvents properties,
it is found useful in science laboratories to cany out qualitative test.
Purification of Water
The need
for water treatment or purification arose to the vast uses in which water is
being employed. The use of water as a solvent could be found useful in science
laboratories for qualities experiment.
Hard water
is not suitable for domestic and laundry purpose except it is treated and the
hardness removed. The natural water, especially the river, ocean, lakes and sea
which are harmful to health, if not removed from water used for domestic and
laundiy purposes.
in water makes the definite properties of water unascertamed, this consequently
result to ambiguous observation and possible wrong interferences which do not
give reliable conclusion of results obtained during the use of such
contaminated waters for laboratory qualitative experiments. These hazards cause
by the qualitative experiments. These hazards cause by the impurities in water,
brings about the need for water purification.
Types of Purifications of Water
There are
various ways in which water can be treated or purified. This largely depends on
the type of impurities in water we wanted to remove and the use we wanted to
employ of water. We have the distillation and the chemical treatment methods of
purification of water.
Distillation is a standard laboratory method of water purification to the
production of pure water called DISTILLED WATER used for quantitative analysis.
It is prepared by condensing water vapour or steam and its thus free from all
solutes and is soft and forms lather with soap, easily. Distilled water is
useful in Distilleries where it is further treated and preserved for use in
hospitals for patients that are short of water in the body. Distilled water as
a form of pure water could be used as drugs to cure many ailments such as skin
diseases, fever, tuberculosis e.t.c. which are health hazards.
water from the distillation process is known to be the purest form
of liquid
water, but it is some what strenuous and costly in obtained. It may also
required subsequent re-distillation of the initial distillate.
Boiling of
Some form
of water which contains simple impurities (such as in temporary hard water) can
be purified by mere boiling. Boiling kills some of the germs, which might be
present in this waters and also coagulate solid impurities including the
hydrogen tri-oxocarbonate (IV) of calcium and magnesium which causes temporary
hardness of water. Boiling of water is difficult to employ in case of large volume
of water, it takes a long time for hydrogen and oxygen ions in water molecules
to orient themselves. Therefore, boiling is not an effective method of water.
It is
realistic that water acquires hardness when it dissolves gypsum (CaSO4.2H20) or
limestone (CaCO3) from the soil over which it flows. Gypsum is then sparingly
soluble in water but that of limestone cannot do so. However, water which
contains carbon (IV) oxide is capable to dissolve small quantities of
limestone. Hard water can also form carbonic acid due to the reactions of
carbon dioxide with water. The process that makes the reaction to take place in
the hardness of water is by the microscopic marine which at ordinary
environment pH exist mostly as bicarbonate ion. Ground water made slightly
acidic by CO2 from the air and from the respiration of soap bacteria which
dissolve the limestone, thereby it acquiring calcium and bicarbonate ions and
becoming “hard”.
If the HC03
concentration is sufficiently great, the combination of processes and the
causes of carbonate which is “lime scale” is to precipitate out on the surface
such as inside of the pipe (calcium bicarbonate itself does not form a solid,
but always precipitates as CaCO3).
water is impure; it usually contains dissolved salts and dissolved
gases, and
sometimes organic matter. Hard water containing cations of calcium magnesium
and iron which are undesirable because they form a precipitate with
soap and react with other substances.
ions: This is the process by which the three divalent cations present in water,
including calcium (Ca2), magnesium (Mg2) and ferrous (Fe2). Hardness ions
develop from dissolved minerals, bicarbonate, carbonate, sulphate abd chloride.
Bicarbonate salt cause temporary hardness, which can be removed by boiling the
water and leaving behind a calcium carbonate solid. Calcium hardness can be
removed by adding excess sodium carbonate to precipitate Ca2 as CaCO3. Hard
water can be passed through an exchange column where hardness ions are captured
on the resin. Removal of hardness is the process called water softening. More
seriously, the calcium and magnesium carbonates tends to precipitates out as
adherent solids on the surfaces of the pipes especially on the hot of heat
exchanger surface of boilers. The resulting scale building can then flow of
heat into the water. It is not only residues heating efficiency but allows the
metals or ions to over heat after it has been pressurized, the systems can now
become catastrophic failure.
Hard water,
as process implies in a substance which will not form lather readily with soap.
It contains a number of dissolved salts, the most important being calcium
tetraoxosulphate (VI), magnesium letraoxosulphate (VI), and calcium hydrogen
trioxocarbonate (IV).
Soap is the
sodium or potassium salt of an organic acid. An ordinary soap
is usually
sodium octadecanoate. When soap is added to hard water, the dissolved salt in
the water will immediately reacts with the soap, molecules.
insoluble calcium and magnesium salt form an unpleasant scum which is wasteful,
as a large amount of soap has to be used in precipitating and removing the
calcium and magnesium ions; after which more soap has used in the actual
In recent
years, this problem has been overcome by the introduction of detergents for
domestic and laundry purposes. These detergents is for domestic used because of
the formation of calcium and magnesium salts to affect by hard water and
soluble in water. When water is agitated with soap, lather is produced. Sodium
stearate is a typical soap. Water derived from natural resources such as rivers
and wells usually contains dissolved solids; these dissolved solids are the
hydrogen carbonate (HCO3) and sulphate ion (S042) of calcium ions and
magnesium. Calcium and magnesium stearate are both soluble in water so that they
precipitate out as a curdy scum. One of the reactions that wastes soap in the
solution for cleansing and produce dirty scum is:
Ca2 +
2C17H35C00 > (C17H35COO)2Ca2
Hard water
is due to metal (minerals) that are dissolved in the water. These minerals
include Ca2, Mg2, Fe2, S042 and HC03. 1-lard water is due to rain moving
through the vast amount of limestone, CaCO3 that occurs in our area to the
aquifer. This is why we measure hardness in terms of CaCO3 the concentration of
any other ion in the water.
Hard Water
is a substance which does not readily form lather with soap due to some ion
contaminations. It is water that contains cations with a charge of 2+,
especially Ca2 and Mg2. These ions do not pose any health threat, but they can
engaged in reactions that leave insoluble mineral deposits, these deposits can
make hard water unsuitable for many uses, and so a variety of mean have been
developed to ‘soften” hard water, that is, removed the calcium and magnesium
Hardness in water is defined as the presence of multivalent cations. Hardness
in water can cause water to form scales and a resistance to soap. It can also
be defined as water that doesn’t produce lather with soap solution.
± Ca2 (C17H35COO)2Ca + 2Na
Rain water
is acidic, because, it combines with carbon (IV) oxide in the atmosphere to
form carbonic acids.
H20 + CO2
> H2C03
if this rain water flows through chalk, chromate rock and limestone, it will
become hard. This is because water react with calcium and magnesium salts in
the rocks.
H2C03 +
CaCO3 – Ca(HCO3)2
hydrogen carbonate also formed in the reaction, which responsible for the
hardness of the rain water.
Softening of Hard Water
Removal of
temporary hardness of water can be easily done by boiling. This hardness is
caused by the presence of dissolved calcium hydrogen trioxocarbonate (IV)
(Ca(HCO3)2 which decomposes on heating by forming calcium trioxocarbonate (IV)
CaCO3, it is insoluble and bring the calcium ions out of the solution and as a
precipitate. Once the calcium ions are out of the solution, the soap that is
added to the water will be available for the formation of lather.
Boil> CaCO3(s) + H20(l) + C02(aq)
hardness can also be removed by using slaked lime, Ca(OH)2
+ Ca(OH)2(s) > 2CaCO3 + 2H20(l)
Slightly soluble Insoluble
Hard water
can also form carbonic acid due to the reaction of carbon dioxide with water.
The minerals deposited are formed by ionic reactions resulting in the formation
of an insoluble precipitate. For example, when hard water is heated, Ca2 ion
react with bicarbonate (HCO3) ions to form insoluble calcium carbonate (CaCO3),
as shown in equation below.
(i) Ca2
(aq) + 2HC03(aq) > CaCO3(s) + H20 — CO2
For large
scale municipal operations, a process known as the “lime—soda process” is used
to remove Ca2 and Mg2 from the water supply. Ions exchange reactions, similar
to those performed in this experiment, which result in the formation of an
insoluble precipitation of slaked lime, Ca(OH)2, and soda ash, Na2CO3, Calcium
precipitates as CaCO3, and magnesium precipitate as Mg(OH)2. These solids can
be collected, thus removing the scale-formation cations from the water supply.
(ii) The
reactions of precipitation of Mg(OH)2 is by consulting the solubility
guidelines in the experiment reveals that the Ca(OH)2 of slaked lime is
moderately soluble in water to give one Ca2 ion and two OH ions for each unit
of Ca(OH)2 that dissolves. The OW ions react with Mg2 ions in the water to form
the insoluble precipitate. The Ca2 ions are unaffected by this reaction, and so
neglected them in the net ionic reaction (equation ii). They are removed by the
separate reaction with C032 ions from the soda ash.
Mg2(aq) +
20W(aq) Mg(OH)(s)
The calcium
carbonate or magnesium carbonate formed is insoluble in water and does not
affect the soft water obtained after boiling as represented in
the below
Ca(HCO3)2 Heat> CaCO3 ± CO2 + H20
Mg(HCO3)2 Hea MgCO3 + CO2 + H20
When the
little quantity of slaked lime is added to the hard water, if it excess the
water will become harder. The slaked lime reacts with the hydrogen carbonate of
calcium or magnesium to form insoluble carbonate of cakiu. r
magnesium as
represented in the equation below.
Ca(HCO3)2 + Ca(OH)2 > 2CaCO3 + 2H20
Mg(HCO3)2 + Ca(OH)2 > MgCO3 + CaCO3 + 2H20
insoluble can be removed by filtration.
Method for the Removal of Temporary and Permanent
Hardness of
temporaly and permanent hardness can be removed by the addition of sodium
carbonate (washing soda) — NaCO3 it is a double decomposition reaction.
+ 2NaCO3 > 2NaHCO3(aq) + CaCO3(s)
carbonate of calcium or magnesium formed is precipitated and removed by
filtration. The filtrate is called the soft water.
2.8 Causes
of Hardness
(i) Calcium
and magnesium salts are responsible for the hardness of water. The calcium
salts are calcium hydrogen carbonate Ca(HCO3)
(ii) It can
also cause by calcium sulphate (CaSO4) and calcium chloride (CaC12).
(iii) The
magnesium salt are magnesium hydrogen carbonate Mg(HCO3)2 and magnesium
chloride (MgCI2). Whenever any of these salts is in the water,
it means
that the water is hard and would no readily lather with soap.
2.9 Determination of Total Hardness of Water
determination of water hardness is a useful test that provides a measure of
quality of water for households and industrial use. Originally, water hardness
was defined as the measure of the capacity of water to precipitate soap. Hard
water is not a health hazard. People regularly take hard water as calcium
supplements. Drinking hard water contributes a small amount of calcium and
magnesium toward the total human dietary needs for calcium and magnesium.
National Academic of Science (1998) states that water be a major contributor of
calcium and magnesium to the diet. Hard water does not cause soap scum, clog
pipes and clog boilers. Soap scum is formed when the scum ion binds with soap.
This causes an insoluble compound that precipitates to form the scum. Soap
actually softens hard water by removing the calcium ions (Ca2) from the water.
When hard
water is heated, CaCO3 precipitates out, which then clogs pipe and industrial
boilers. This led to the malfunction or damage and is very expensive to remove.
(A) Water
Softeners: When there is hard water, water softener can be used to remove the
hardness, salt is mixed with water. The sodium ion from salt replaces the
calcium ion, but this causes the water to be too salty for drinking.
Complexometric Titration: Permanent hardness is usually determined by titrating
it with a standard solution of ethylene diamine tetra acetic acid (EDTA) which
is used for the estimation of stable cations. It is a completion or chelating
agent used to capture the metal ions. This causes the water to be softened, but
the metal ions are not removed from the water. EDTA simply binds the metal ions
to it very tightly. It is also versatile chelating agent. Chelating agent is a
substance whose molecules can form several bonds to a single metal ions. It is
also the substance that binds with a metal ion to form a metal ion which
results in complexion.
Multidentate Ligands Method: There are many clawed holding onto metal ion to
form a very stable complex. EDTA can form four or six bonds with a metal ion.
of Hard Water
One of the
most outstanding characteristics of hard water is its reaction with soap. If
distilled water or soft water is shaken with a solution of soap or lather, foam
is formed immediately, a dilute solution of soap be added drop by drop to some
hard water in a bottle which is stopped and shaken after each addition. it will
be found that no lather formed at first. The water is at the same time; assume turbidity
is due to the formation of an insoluble precipitate. Finally after sufficient
soap has been added, lather will appear. Soap are sodium or potassium salts of
fatty (C17H35COONa) of high molecular weight are soluble in water, but those of
calcium and magnesium are not in hard water, the ions of these elements
displace the sodium, giving precipitates of that soluble fatty acids salts.
Na4 + CaSO4 > (C17H35COO)2Ca2 + Na2SO4
Advantages of Hard Water
Prevention of Lead Poison: Very soften water tends to dissolve the lead pipes.
The accumulative poison and continual drinking of the water produce lead
poisoning. But hard water reduces the amount of lead dissolved in a given
volume of water.
Health: Hard water contains calcium compounds which can be found in building of
bones and teeth.
Brewing: Hard water is designable in the industries.
Drinking: Since the bi-carbonate gives a refreshing taste to water. and water
is good for drinking.
Disadvantages of Hard Water
(i) Boiler
Scale: Pipes are blocked and fuel wasted as a result of occurrences
of boiler
scale inside the water pipe due to the action of hard water on them.
Laundry Work: It wastes soap and the salt formed changes materials.
Industries: This is a nuisance in industries by paper and photograph.
In this
research work, complexometric titration is employed in the determination of
Total hardness. pH of the water collected from different areas in Kajola. Odo —
Oja and Araromi areas in Ikere Ekiti, Ekiti State
were taken using pH meter.
Determination of Water Hardness with Ethylene Diamine Tetra-acetic Acid (E. D.
T. A.)
Water hardness, due to Ca2 and Mg2 is expressed as mg/I CaCO3
(ppm). The
total of Ca2 andMg2 is titrated with standard EDTA using an
Black T indicator. A standard EDTA solution is prepared from dried
(do not
exceed 80°C) Na2H2Y.2H20 (purity 00.0 ± 0.5%). if the sample does not contain
magnesium, Mg — EDTA is added to the titration flask to provide a sharp
end—point with Eriochrome black T, since calcium does not form a sufficiently
strong chelate with the indicator to give a sharp end—point.
Ca +Mg
> CaY +Mg End point: Mg2 ± H1n2 > Mgln + W
MgIn + H2Y2
> MgY2 + HIn2 ±
{ Red} {
Colourless} { Colourless} { Blue} The free acid parent to the indicator is H31n
and that titrant EDTA H4Y.
Diamine Tetra-acetic Acid (EDTA) forms stable complexes with many metal ions, e
g Ca2 and Mg2 in aqueous solution This is done by reacting one mole of EDTA
molecules quantitatively with one mole of metal ion e.g.
Ca2(aq) +
EDTA (aq) > {CaEDTA}2(aq)
3.2 Water
Sample Collection
Water (H20)
was collected at six different locations in Kajola, Odo — Oja and Araromi areas
in Ikere Ekiti, Ekiti
State. The water was
collected in a securely covered plastic containers filled to the brim. Each
container was labeled accordingly to indicate the point of collection.
The pH and
Total Hardness were determined using E.D.T.A. with Eriochrome Black T indicator.
The standardization of EDTA solution was done.
Hardness: Determination of Total Hardness (Ca2 and Mg2) of water samples from
the locations were carried out with Ethylene Diamine Tetra-acetic Acid (EDTA),
as chelating agent with Eriochrome black T indicator. The most widely used
chelating agent in titrations is Ethylene Diamine Tetra-acetic Acid
Result of
the Experiment and Calculations Involved: The results of titration to determine
the Total Hardness (Mg2 and Ca2 ) in different well water sources or locations
using EDTA were tabulated in the next chapter. Also the pH for each well water
source was determined.
of Total Hardness using E.D.T.A. with Eriochrome Black T
5Oml of aliquot of the water sample was pipetted into a conical flask, add 2m1
of the buffer solution O.05m1 of the mg-EDTA solution, and add few drops of the
indicator solution. Then titrate with 0.0 1M EDTA until the colour changes from
wine to red to a pure blue colour.
of EDTA So’ution: The most widely used chelating agent for titration is
Ethylene Diamine Tetra-acetic Acid (EDTA).
for Hardness Determination: 25m1s of the water sample was pipetted into a clean
conical flask. Then 2rnls of buffer solution and 5 drops of Eriochrome black T
indicator was added. Then titrate with 0.O1M EDTA until the colour changes from
wine to a pure blue colour.
3.3 pH
Electric pH
meter (Digital) Jenway Model 3010 was used in the survey at the site of
collection. It has combined an electrode which was standardized with two buffer
solutions pH 4 and pH 7. The temperature of solution was taken and pH meter
adjusted manually to solution temperature. The electrode was dipped into the
water sample after standardizing pH recorded and electrode minsed with
distilled water and dried in between sample measurement. The readings were
taken for each water sample.
4.2 Result
of Analysis of Different Well Water Sources
The results
of analysis of hardness and pH of well water collected at different locations
in Ikere Local Government Area, Ekiti
State are presented in
the table below:
Table VIII:
Table of Results
Well Water Sources
pH Values
(Area A)
(Area B)
Odo — Oja
(Area A)
7. 27
Odo — Oja
(Area B)
(Area A)
6. 11
(Area B)
Hard water
increases soap consumption in laundry and so the type of water to be used in
washing cloth should be water with low hardness values.
shows that well water samples from Odo — Oja are the best for both laundry and
domestic use. Also it is the best well water under case study that is good
source of drinking if undergo microbiological and other chemical analyses.
It is more
preferable to use well water from Odo — Oja with low hardness values ranging
from 20.6 to 25.2pp and pH values ranging from 6.96 to 7.27 since much money
will not be spent on purchase of soap in our homes.
5. 1
From the
analysis. the result shows that well water sample from Odo — Oja is the best
for both laundry and domestic purpose because the level of hardness is very low
(20.6 — 25.2ppm). Also this water can be a good source of drinking if undergoes
microbiological and other chemical analyses.
Also it is
preferable to use well water from Odo — Oja areas with hardness ranging from
20.6 to 25.2ppm and pH values ranging from 6.96 to 7.27 for laundry purpose,
since much money will not be spent on buying soap thereby enhancing its
economic value.
It is
recommended that well water from Odo Oja area in Ikere Local
is the best for both laundry and drinking purpose. The hardness values ranged
from 20.6 to 25.2pp and pH ranging from 6.96 to 7.27 makes it a  very good source of water for drinking as it
falls within the permissible level of WHO standards.
The low
level of hardness also enhances its economic values in laundry purpose as much
money will not be spent on soap as water in this area is not as hard as well
water from Araromi and Kajola areas.
Since the
project cover only raining season, it is recommended that more research should
be carried out to ascertain the quality of the water throughout the year.
Afolayan S.
A (1986): Chemistry Senior Secondary Schools. Macmillan Publisher.
(1979): Certificate Chemistry, Third Edition. Hazeld Watson and Viney Limited.
Pg 202 206.
Douglas A.
Skoog and Donald M West (1975): Fundamentals of Analytical Chemistry. Third
Edition. Holt — Saunders International Edition. Pg 737 — 738.
Gary D.
Christian (2008): Analytical Chemistry. Sixth Edition, Willey Student Edition.
Pg 742 — 743.
(1996): Quality Assessment of Domestic Water Sources.
Boyle (1977): Analytical Chemistry.
Stephen A.
Afolayan (1986): A New Certification Chemistry for Senior Secondaiy
School, 2nd Edition.
Published (1989). Pg 32 — 33.
Venon L.
S., & David J. (1980): Water Chemistry. Pg 3 — 6
Preparation of O.OIM EDTA Solution: Dry the purified dehydrate (Na2H2Y.2H20) at
80°C to remove superficial moisture. After cooling, weigh about 3.8g (to the
nearest milligram) into a i-litre volumetric flask, dilute to the mark with
distilled water.
Preparation of the Magnesium complex of EDTA 0. 1M Solution: To 37.2g of
N2H2Y.2H20 in 500m1 of distilled water, add an equivalent quantity (24.65g) of
M8SO4.7H20. Introduce a few drops of phenolphthalein followed by sufficient
sodium hydroxide to turn the solution faintly pink. Dilute the solution to
1—litre. When properly prepared, portion of this solution should assumed a dull
violent colour when treated with pH- 10 buffer and few drops of Eriochrome
black T (ErioT) indicator. Furthermore, a single drop of 0.0lNaHY should cause
a colour change to blue, while an equal quantity of 0.01 Mg should cause a
change to red. The composition of the solution should adjust by addition of Mg2
or Na2H2Y until these criteria are met.
Preparation of Eriochrome Black T Solution: Dissolve 200mg of the solid in a
solution consisting of 15m1 of triethanolamine and 5m1 of absolute ethanol.
Solution should be freshly prepared every two weeks, refrigeration slow their
Preparation of Buffer Solution, pH 10: Dilute 570m1 of aqueous NH3 (sp gr 0.90)
and 70g of NH4C1 to approximately 1-liter.
Preparation of NH3-NH4CI Buffer Solution, pH 10: Dissolve 3.2g N1-LCI in water,
add 29m1 conc.NH3 and dilute to about 50m1. The buffer solution is best for long
period of time in a polythene bottle to prevent leaching of metal ions from


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