A H M 531 Alkalinity By: Mu'men Al-Otoom
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A H M 531 Alkalinity By: Mu'men Al-Otoom
Introduction :
There are many different between acidity & alkalinity :
Acidity Alkalinity
Titrant NaCO3 H2SO4
The direction Increase PH Decrease PH
travels of PH
Indicator M.O. & Ph.Ph. Ph.Ph. & M.O.
Causes CO2 & Mineral OH- , CO3-2 &
organic HCO3-1
Use to To measure the ability of To measure the ability of
solution to neutralize solution to neutralize
bases acids
Classification Only one case Five cases
Chemistry :
OH- : Hydroxide alk.
CO3-2 : Carbonate alk.
HCO3-1 :Bicarbonate alk.
General discussion :
The alkalinity of water is a measure of it’s capacity to neutralize
acids to except in the case of specific pollution discharge. Is in
reaction due to the presence of bicarbonates formed in reaction in the
soils through which natural waters percolate. However hydroxide
and carbonate may also be present in natural water, particularly
those which are eutrophic , and this fact will tend to be reflected in
higher PH values .
TOOLS :
1) Burette .
2) Flasks .
3) pH meter .
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A H M 531 Alkalinity By: Mu'men Al-Otoom
Procedure : ( Tap water )
1. Put in the flask 100 ml .
2. Take the PH record by PH meter .
3. Put the indicator
A. methyl orange : if 4.5 < PH record < 8.3 .
B. phenolphthalein then Methyl orange : if PH record >8.3 .
4. Using titration by sulphuric acid ( H2SO4 ) .
5. when the sample become orange record the volume of acid which
needed to neutralized alk. .
Procedure : ( Unknown solution )
1. Put in the flask 100 ml .
2. Take PH record before titration ( V H2SO4 = 0 )
3. Put the indicator
A. methyl orange : if 4.5 < PH record < 8.3 .
B. phenolphthalein then Methyl orange : if PH record >8.3 .
4. Using titration by sulphuric acid ( H2SO4 ) .
5. When the color change from pink to colorless (@ 8.3 ),the volume
of H2SO4 that you used is V1 .
6. When the color change from yellow to orange (@ 4.5 ), the volume
of H2SO4 that you used is V2 .
7. The total of alkalinity = V1 + V2 .
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A H M 531 Alkalinity By: Mu'men Al-Otoom
There is a dosage way to classification the alkalinity :
This way depend on previous volumetric analysis ( we need V1 & V2 )
There are five cases :
Vt = Total volume of alkalinity .
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A H M 531 Alkalinity By: Mu'men Al-Otoom
CALCULATION :
Alkalinity = A x N x 50000
100
A : Titrant volume .
N = Normality of H2SO4 = 0.02 .
Procedure : ( Tap water )
PH =
Vol. of H2SO4 = 19 mL
Alkalinity = ( 19x 0.02 x 50000 ) = 190 mg/L as CaCO3
(100 )
Procedure : ( Unknown solution)
PH Vol. of H2SO4
9.5 0
9.4 0.5
9.4 1.0
9.3 1.5
9.3 2.0
9.1 2.5
9.0 3.0
8.8 3.5
8.6 4.0
8.5 4.1
8.4 4.2
8.2 4.3
8.0 4.5
7.9 5.0
7.4 5.5
7.3 6.5
7.1 7.5
6.7 8.5
6.6 9.5
6.4 10.5
6.3 11.5
6.1 12.5
6.0 13.5
5.8 14.5
5.7 15.5
5.6 16.5
5.5 18
4.8 19.5
4.7 20
4.3 20.5
3.8 21
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A H M 531 Alkalinity By: Mu'men Al-Otoom
V1 = 4.55 ml .
Alkalinity = ( 4.55 x 0.02 x 50000 ) = 45.2 mg/L as CaCO3
(100 )
V2 = 20.455 – 4.55 = 15.91 ml .
Alkalinity = ( 15.91 x 0.02 x 50000 ) = 159.1 mg/L as CaCO3
(100 )
Total Alk. = 45.2 + 159.1 = 204.3 mg/L as CaCO3
Resultant : ( as second way )
You can see :
V1 < V2 →→→→ Case 4
-2 -1
☺ It has CO3 , HCO3 alk.
Vol. of CO3-2 = 2 (V1) = 9.1 mL
Vol. of HCO3-1 = ( V2 – V1 ) = ( 15.91 – 4.55 ) = 11.36 mL .
Alkalinity of CO3-2 = ( 9.1 x 0.02 x 50000 ) = 91 mg/L as CaCO3
(100 )
-1
Alkalinity of HCO3 =( 11.36 x 0.02 x 50000 ) = 113.6 mg/L as CaCO3
(100 )
Total Alk. = 113.6 + 91 = 204.3 mg/L as CaCO3 .
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