Seventh Experiment: Acid-Base Titration
(Classical Titration)
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Lab. 7, Experiment 7
Neutralization Titration
Neutralization titration is a volumetric analytical approach. It applies acid/base reaction to
determine the concentration of acid/base using a standard solution of base/acid. Classical
neutralization titration usually uses an external indicator.
Objective
To determine the concentration of hydrochloric acid
Equipments and Materials:
100 or 50 mL butrtte, 25 mL pipette, 250 mL Erkenmeyer flask, phenolphthalein (Phph) and
methyl orange (MO)
Procedure:
1. Fill a 100 mL or 50 mL burette with a standardized solution of 0.1 M NaOH.
2. Transfer accurately 25 mL of the analyte (HCl) using a pipette to the Erlenmeyer flask
3. Add 2-3 drops of phenolphthalein to HCl in the Erlenmeyer flask. (what is the color of
the solution?)
4. Add NaOH from the burette slowly to HCl in the Erlenmeyer flask. During addition
shake the mixture carefully.
5. Stop the addition of NaOH as soon as you observe stable pink color.
6. Pepeat the titration process twice with adding NaOH drop by drop when you about to
reach the end point.
Note: In a titration process, one drop of a solution from a burette changes the color
of a mixture in Erlenmyer flask, which is the end point
7. Record the initial and final volumes of the last two titrations.
8. Repeat steps 6 and 7 with using MO instead of Phph.
Calculations:
1. Calculate the added volume of NaOH for each titration.
2. Calculate the average of the added volume.
3. Calculate the concentration of HCl using the equation bellow. (Observe the variation of
color in acidic and alkaline media).
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4. Calculate the % of error =
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Lab. 7, Experiment
Report on Neutralization Titration
Student name: #.
Date:
Using Phph Using MO
Trial 1 Trial 2 Trial 3 Trial 4
Initial volume
Final volume
Added volume
Average
CHCl(M)
% of error
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Experimental 8
Complexometric Titration using EDTA
(I)Preparation and Standardization of EDTA Solution
Principle
EDTA solutions are usually prepared by weighing the dehydrated disodium salt of
ethylene diamine tetra acetic acid.
Preparation of 0.1M Solution of EDTA:
Dissolve 37.225 gm of analytical reagent (A.R.) disodium dihydrogen ethylene
diamine tetra acetate dihydrate in water and dilute to one liter.
Metal ion indicators used in these titrations:
The requisites of a metal ion indicator for use in the visual detection of end points
include:
1- The color detection must be such that before the end point when
nearly all the metal ion is complexed with EDTA, the solution is
strongly colored.
2- The color reaction should be specific or at least selective .
3- The metal-indicator complex must be less stable than the metal -
EDTA complex to ensure that at the end point, EDT A removes metal
ions from the metal indicator complex. The change in equilibrium from
the metal indicator complex to metal EDTA complex should be sharp
and rapid.
4- The color contrast between then free indicator and the metal indicator
complex should be such as to be readily observed.
5- The indicator must be very sensitive to metal ions so that the color change occurs as
near to the equivalence point as possible.
I-Standardization of EDTA solution against MgSO4 .7H2O
Procedure:
1- Pipette 10 m1 of the MgSO4 solution into a 250 ml conical flask, then add 50-60
ml of distilled H2O and 3 ml of buffer (pH=10) .
2- Add about 3 or 4 pieces of Eriochrome black T indicator and titrate with the
EDTA solution until the wine red color changes to clear blue.
Calculations:
Calculate the molarity of EDTA
M .V (MgSO4)= M' .V' (EDTA)
0. 1 x 10 = M' .V' (Volume taken from burette)
