hardness of water & its determination

1. PRESENTATION ON
“HARDNESS OF WATER
& ITS DETERMINATION”

2. ACKNOWEDGEMENT
I owe a great many thanks to a great many people who
helped and supported me during the writing of this
assignment.
My deepest thanks to lecturer, the guide of the project, for
guiding and correcting various documents of mine with
attention and care.
I would also thanks my institution and my faculty members
without whom this project would have been a distant
reality. I also extend my heartfelt thanks to my family and
well wishers.

3. Constituents-
2 elements of
H2
1 element of
O2
3 states of
water-
Solid, Liquid & Gas
Occurrence-
Most abundant
& widely
distributed
3/4th of
Earth’s crust

5. STRUCTURE
• H20 is Polar i.e. ,it is partially charged
• O2 has higher Electronegativity
• H2O is a solvent
• Forms 104.5deg angle
• Bent shape/V-shape structure
• H-bonding

6. HARDNESS OF WATER
Soap consuming power of water is called Hardness.
Ca2+/Mg2+ cationsCause Hardness
SoapSodium/Potassium salts of oleic acid,
palmitic acid, stearic acid.
2C17H35COONa + CaCl2  (C17H35COO)2Ca +2NaCl
(Sodium stearate)
2C17H35COONa + Ca(HCO3)2 (C17H35COO)2Ca + 2NaHCO3
Calcium stearate
(Insoluble salt)

7.  There are two types of hardness-
 Temporary hardness
 Permanent hardness
1>Temporary hardness-
~it is due to the presence of soluble salts of HCO3-
of Ca & Mg.
~it can be removed by boiling. In this the HCO3- are
decomposed into insoluble CO32-
Ca(HCO3)2CaCO3 + H2O + CO2
(soluble) (insoluble)

8.  2. Permanent hardness
It is due to sulphides,chlorides &
nitrates of calcium, magnesium & other metals.
CLASSIFICATION OF HARDNESS
Alkaline hardness Non-alkaline hardness
carbonates,bicarbonates chlorides,sulphides &.
& hydroxides of metals nitrates of metals

9.  1.SOAP SOLUTION METHOD:
Ca(HCO3)2+2C17H35COONa(C17H35COO)2Ca +NaHCO3
Ca bicarbonate sodium stearate Ca stearate
CaCl2 +2C17H35COONa(C17H35COO)2Ca+2NaCl
CaSO4+2C17H35COONa(C17H35COO)2Ca+Na2SO4

10.  Hardness causing metal ions get
precipitated.
 When more sodium salt is added, lather
is formed.
 The aliquot is titrated against standard
soap solution in alcohol.
 End point indicates total hardness.
 The aliquot is boiled for 30 mins.
 Temporary hardness get removed(may
be due to the formation of CO2 which
escapes)

11.  2.EDTA method:
Burette:Na2[EDTA]H2[EDTA]H2
2- +2Na+
Flask:Ca2+/Mg2++[EBT]H[EBT]Ca +H+
(blue) (wine red)
Titration:
[EDTA]H2
2-+[EBT]Ca[EDTA]Ca+[EBT]H {end point}
(wine red) colorless blue

12.  Boil the aliquot for 30mins
 Temporary hardness is removed
 The remaining again titrated against
Na2[EDTA]H2 complex
 End point indicates permanent hardness
{Total hardness-Permanent hardness=temporary
hardness}

13.  Blockage of passage occurs when water is used for
cooling due to scale deposition.
 Hard water is harmful for drinking as it causes
deposition of calcium in the bone joints.
 It causes formation in boilers and pipes.
 Hard water does not form any lather with soaps or
detergents.

14.  Hard water is calculated in terms of calcium
carbonate. It is because of the following reasons:
 Molecular weight of CaCO3 is:
40+12+16x3=100
 Most insoluble salt of Ca which is precipitated
during water treatment processes.
 Equivalent of CaCO3 =
=[Mass of hardness producing substance x chemical equivalent of CaCO3
Chemical equivalent of hardness producing substance
= [Mass of hardness producing substance in mg/L]x multiplication factor