Environmental lab Lab 4 alkalinity –acidity and determination of alkalinity in water experiment at JORDAN UNIVERSITY OF SCIENCE AND TECHNOLOGY by: ANAS MAGHAYREH

1. Jordan University of Science and Technology
Faculty of Engineering
Civil Engineering Department
CE 453
“Environmental lab”
“Alkalinity –acidity and determination of alkalinity in
water”
Experiment (4)
Student Name: Anas Mohammad Maghayreh.
Student ID: 20120023117.
Section #:1
Submission Date: 26/7/2015.
Submitted to: Dr. Hani Abu Qdais

2. *Abstract:
Alkalinity is the ability of water to resist change in PH, which is due to
presence of certain species such as hydroxide ions OH-1
, bicarbonate ions
HCO3-1
and carbonate ions CO3-2
,
In this experiment we will calculate
Total Alkalinity = [HCO3ˉ1
] + 2[CO3ˉ²
] + [OHˉ1
] – [H+
]
Carbonate ALK=[CO-2
]+[OH-1
]-[H+
]-[H2CO 3]
Caustic ALK=[OH-
]-[H+
]-[HCO-
]-2[H2CO 3]
The alkalinity of water can be determined by titrating the water sample with
Sulphuric acid of known values of pH, volume and concentrations. Based on
stoichiometry of the reaction and number of moles of Sulphuric acid needed
to reach the end point, the concentration of alkalinity in water is calculated.
*Introduction:
Alkalinity is primarily a way of measuring the acid neutralizing capacity of
water. In other words, its ability to maintain a relatively constant pH. The
possibility to maintain constant pH is due to the hydroxyl, carbonate and
bicarbonate ions present in water. The ability of natural water to act as a
buffer is controlled in part by the amount of calcium and carbonate ions in
solution. Carbonate ion and calcium ion both come from calcium carbonate
or limestone. So water that comes in contact with limestone will contain high
levels of both Ca++
and CO3
2-
ions and have elevated hardness and alkalinity.
In the other hand the ENVIRONMENTAL SIGNIFICANCE occur as
following
Alkalinity is important for fish and aquatic life because it protects or buffers
against rapid pH changes. Higher alkalinity levels in surface waters will
buffer acid rain and other acid wastes and prevent pH changes that are
harmful to aquatic life.
Large amount of alkalinity imparts bitter taste in water.
The principal objection of alkaline water is the reactions that can occur

3. between alkalinity and certain cations in waters. The resultant precipitate can
corrode pipes and other accessories of water distribution systems.
In wastewater treatment, alkalinity is an important parameter in determining
the amenability of wastes to the treatment process and control of processes
such as anaerobic digestion, where bicarbonate alkalinity, total alkalinity,
and any fraction contributed by volatile acid salts become considerations.
*Objective :-
To be familiar with the concepts of alkalinity and acidity, and the
measurement of alkalinity in water.
*Procedure:
1- Pipet exactly 100 ml of sample into porcelain dish and drop in a
magnetic rod.
2- Mount a 25-ml burette and fill it to the mark with 0.02M sulfuric acid
solution.
3- Add 5 drops of phenolphthalein indicator to the sample. if the solution
turns pink ,add acid’s slowly till pink color disappears . Record the volume as
Vp.
4- Add 5 drops of Methyl orange indicator to the same sampling at the end
of first titration and add 0.02 M sulfuric acid slowly till orange color turns to
pink.
*Apparatus
1- Burettes, 25 ml
2- Porcelain dish
3- Magnetic stirrer and rod.
4- Beaker, 150 ml.
5- Pipet
6- Measuring cylinder
7- pH meter

4. *Sample:
Tap water sample, Methyl orange, Phenolphthalein.
NaOH (0.02 N)
H2SO4 (0.02 N)
Picture (1): Apparatus Required
Picture (2): Chemical Required

5. Picture (3): Procedure chart

6. *Results and Calculations:
100 ml from water
PH=10.3 “ phph from pink to colorless “
V sulfuric acid = 13 ml = A1
Phenolphthalein Alkalinity (in mg/L as CaCO3) = (A1×N
×50,000 ) / V
= (13*.02*50000)/100
= 130 mg/L as CaCO3
PH=4 “ M.O
V s = 15.5 ml
- A = 13 + 15.5 = 16 ml
Total Alkalinity (in mg/L as CaCO3) = (A×N ×50,000 ) / V
= ( 28.5 * 0.02*50000)/100
= 285 mg/L as CaCO3

7. *Discussion:
In our experiment when we were added so4 to tap water (and drop of ph.ph) the
color of the indicator didn't change that’s mean water can be used as drinking
water and pH above 8,3 ,but when the indicator (Methyl orange ) the color change
from orange to yellow and the volume of so4 equal(24 ml) and PH under 8,3.
Phenolphthalein is often used as an indicator in acid–base titrations. For this
application, it turns colorless in acidic solutions and pink in basic solutions.
At the second stage we used (NaOH) and when we added so4(phenolphthalein as
indicator which change from yellow to pink color) volume of so4 (7 ml), and when
(Methyl Orange used as indicator )the volume of so4(20 ml) so the total volume
equal (27 ml)
).-
)and(OH3of (CaCOAnd we can find the alkalinity
Why is alkalinity reported as "mg/L as CaCO3"?
Units of mg/L are a “mass dissolved in a liquid.” Reporting alkalinity as “mg/L as
CaCO3” specifies that the sample has an alkalinity equal to that of a solution with a
certain amount of calcium carbonate (CaCO3) dissolved in water. The alkalinity test
does not actually measure a mass per volume.
Alkalinity, or “acid neutralizing capacity,” is measured by adding acid to the sample
and figuring out the equivalent alkalinity in the water. The actual units for the
alkalinity titration are moles or equivalents per volume (moles/L or eq/L). Converting
alkalinity from eq/L to “mg/L as CaCO3” takes into account that one mole of
carbonate (CO3
2-
) can neutralize 2 moles of acid H+
).
The units of “mg/L as CaCO3” are for convenience only, allowing you to consider
how much CaCO3 you would need to create a solution with the same alkalinity as
your sample.
The factor of 50,000 is used because alkalinities are commonly
expressed in terms of milligrams per liter of equivalent calcium
carbonate. Calcium carbonate has a formula weight of 100g/mole. Since it

8. has two equivalents per mole we must divide this by two to get 50
g/equivalent or 50,000 mg/equivalent.
*The results was not accurate as required due to the following:
 Some personal errors during the experiment.
 May be an error while adding the acid.
 Errors in the calculation.
*Conclusion:
The alkalinity of water can be determined by titrating the water sample
with Sulphuric acid of known values of pH, volume and concentrations.
Based on stoichiometry of the reaction and number of moles of Sulphuric
acid needed to reach the end point, the concentration of alkalinity in water
is calculated. When a water sample that has a pH of greater than 4.5 is
titrated with acid to a pH 4.5 end point, all OH-, CO3
2-,
and HCO3-
will be
neutralized. For the pH more than 8.3, add phenolphthalein indicator, the
color changes to pink color. This pink color is due to presence of hydroxyl
ions. If sulphuric acid is added to it, the pink color disappears i.e. OH-
ions
are neutralized. Then add mixed indicator, the presence of CO3
2-
and
HCO3-
ions in the solution changes the color to blue. While adding
sulphuric acid, the color changes to red, this color change indicates that all
the CO3
2-
and HCO3-
ions has been neutralized. This is the end point.
From our experiment we were able to get familiar with the concept of
alkalinity and acidity and the measurements of alkalinity in water.
We were also able to define the alkalinity as the neutralizing of acids.
We also noted that PH decreases as we add more acid.
*References:-
*Sanitary LAB. Manual (Experimental Water Quality Engineering).
*The LAB Lecture note.
*Wikipedia (chemistry and environmental lab experiments)