LAB # 07
STATEMENT:
To determine Alkalinity of given water samples by Titration using the Phenolphthalein and Methyl
Orange indicator method.
OBJECTIVES: Write down the objective of this Lab
APPARATUS:
 Burette
 Pipette
 Erlenmeyer flask
 Measuring cylinder
 Porcelain dish
 Volumetric flask
 Magnetic stirrer and rod
REAGENTS:
 Sodium hydroxide (NaOH)
 Phenolphthalein indicator
 Hydrochloric acid (HCl)
 Distilled water
RELATED THEORY
Introduction:
Carbonate is an important anion present in natural waters and its concentration can affect the pH and
alkalinity of the water. The aim of this lab report is to determine the concentration of carbonate in a
water sample using the titration method. The WHO guidelines for drinking water suggest that the
acceptable limit of carbonate concentration in drinking water is 100 mg/L. In this experiment, we will
use the titration method to measure the concentration of carbonate in a water sample and compare it
with the WHO guideline.
Bicarbonate is an important anion present in natural waters, and its concentration can affect the pH
and alkalinity of the water. The aim of this lab report is to determine the concentration of bicarbonate
in a water sample using the titration method. The WHO guidelines for drinking water suggest that the
acceptable limit of bicarbonate concentration in drinking water is 250 mg/L. In this experiment, we
will use the titration method to measure the concentration of bicarbonate in a water sample and
compare it with the WHO guideline.
WHO guideline:
Content of alkalinity
Carbonate
Bicarbonate
ppm as per WHO Standards
Source of Carbonate and Bicarbonate in Ground Water:
Carbonate is formed by the dissolution of carbonate rocks such as limestone and dolomite. The
concentration of carbonate in natural waters can vary depending on the geology of the region.
Carbonate can also be produced by the reaction of bicarbonate with water at high temperatures and
pressures.
Bicarbonate is one of the major anions present in natural waters, and its concentration can vary
depending on the geology of the region. Bicarbonate is formed by the dissolution of carbonate rocks
such as limestone and dolomite. It can also be produced by the reaction of carbon dioxide with water
in the atmosphere, which can then dissolve into groundwater.
Procedure:
 We first prepared a standardized HCl solution of 0.1 M by dissolving HCl in distilled water.
 We collected a water sample of 50 ml from a nearby stream using a pipette and transferred it to
an Erlenmeyer flask.
 A few drops of phenolphthalein indicator were added to the flask, and the solution turned pink.
 We slowly titrated the water sample with the HCl solution from the burette while stirring
continuously until the pink color disappeared.
 We continued adding HCl until the solution turned a permanent pink color, indicating the end
point.
 We recorded the volume of HCl used for titration and repeated the titration process at least two
more times to get an accurate measurement.
 We then prepared a blank solution of distilled water and titrated it using the same method to
determine the amount of HCl used to neutralize the carbon dioxide present in the air.
 We calculated the concentration of bicarbonate ions using the formula:
 Concentration of bicarbonate ions = (B - C) x M / V
 Where B is the volume of HCl used to titrate the water sample, C is the volume of HCl used to
titrate the blank solution, M is the molarity of HCl, and V is the volume of the water sample in
liters.
 To determine the concentration of bicarbonate ions, we added NaOH to the water sample to
convert the bicarbonate ions to carbonate ions. We then repeated the titration process using HCl
to titrate the carbonate ions.
 We recorded the volume of NaOH used to neutralize the bicarbonate ions and used the following
formula to calculate the concentration of bicarbonate ions:
 Concentration of bicarbonate ions = (B - C) x M / V
OBSERVATIONS AND CALCULATIONS:
Sample
No
Sample
ID
Location
Latitude
Longitud
e
Alkalinity
(mg/l)
Remarks
DISCUSSION: Discuss the results of this Lab. Add Excel graphs of alkalinity with permissible limits
defined by WHO Standards. Also, add GIS-based spatial disparity maps of alkalinity.
CONCLUSIONS:
REFERENCES: