Learn about the preparation and standardization of 0.05 M EDTA solution through a laboratory experiment or practical.
Aim:
To prepare and standardize 0.05 M EDTA solution using calcium chloride.
Requirements:
Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.
Chemicals: LR grade disodium edetate (EDTA), ammonia (NH3), calcium chloride (CaCl2), ammonium chloride (NH4Cl), hydrochloric acid (HCL), and solochrome black-T indicator, etc.
Apparatus: Digital/analytical balance, and Ultrasonicator.
Principle:
The standardization of EDTA solutions is based on complexometric titration. When the indicator is introduced to a calcium chloride solution, the Ca-indicator complex forms. When titrating against disodium edetate, the complex converts calcium to EDTA, releasing a blue-colored indicator, indicating the reaction's endpoint.
The following is the reaction that is involved in this titration.
Preparation of 0.05 M EDTA solution:
Take 18.16 gm of EDTA and dissolve in 300 ml of distilled water in a volumetric flask, and properly mixing it. Once it has completely dissolved, make up the volume to 1000 ml.
Preparation of 0.05 M calcium chloride:
Take 07.35 gm of CaCl2 and dissolve in 500 ml of distilled water in a volumetric flask, and properly mixing it. Once it has completely dissolved, make up the volume to 1000 ml.
Preparation of 1 M ammonia solution:
Take 75.00 ml of ammonia (Strong) using a pipette, dilute in 100 ml of distilled water in a volumetric flask, and properly mixing it.
Preparation of ammonia buffer of 10 pH:
Take 05.40 gm of NH4Cl, and 35.00 ml of 10 M ammonia solution and dissolve in 100 ml of distilled water in a volumetric flask and properly mixing it.
Titration procedure:
- All glassware should be cleaned and dried according to standard laboratory procedures.
- Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
- Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
- Remove air bubbles from the burette and adjust the reading to zero.
- Take 10.00 ml of calcium chloride solution and pour it into a conical flask.
- To make it alkaline, add 05 mL of buffer solution previously adjusted to pH 10.
- Add 2 drops of solochrome black-T indicator.
- Titrate the sample solution with EDTA until the endpoint is reached. The actual endpoint is indicated by a change in the color of the solution.
- Properly record the readings of the burette.
- To get accurate results, repeat the titration three times.
- Take their mean and calculate the molarity of EDTA.
Observation table:
|
Sr. No. |
Content
in conical flask |
Burette
reading |
Volume
of titrant used (ml) |
|
|
Initial |
Final |
|||
|
1 |
|
|
|
|
|
2 |
|
|
|
|
|
3 |
|
|
|
|
|
Mean: |
|||
Calculations:
M1V1= M2V2
M2 = V1 M1 / V2
Where,
M1 is molarity of calcium chloride
V1 is volume of calcium chloride
M2 is molarity of disodium edetatesolution.
V2 is volume of disodium edetate solution used
Result:
The strength of the prepared EDTA solution was found to be_____M.
Commonly asked questions on titration of EDTA are as follows.
Why buffer solution is used in EDTA titration?
In EDTA titration, a buffer of ammonium chloride (pH 10) is used as it resists pH change. This is since all reactions involving metal ions and EDTA are pH-dependent.
Why do we standardize the EDTA solution?
Standardization of a prepared EDTA solution is performed to determine its exact molarity.
Which indicator is used in standardizing EDTA?
Eriochrome Black T indicator is used in the complexometric EDTA titration which produces color change from blue to pink.
You may also like this
No comments:
Post a Comment