Learn about the preparation and standardization of 0.1 n NaOH solution using succinic acid through a laboratory experiment or practical.
To prepare and standardize 0.1 n NaOH using succinic acid as a primary standard
Requirements:
Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, wash bottle, etc.
Chemicals: LR grade sodium hydroxide (NaOH), succinic acid (C4H6O4), phenolphthalein indicator, etc.
Apparatus: Digital/analytical balance
Theory:
Solid NaOH can't be used as a primary standard as it can't be available in a pure form. This is because it absorbs moisture and carbon dioxide from the air when it is stored and also when it is weighed.
This reaction consumes hydroxide ions, changing the concentration of a standard sodium hydroxide solution. Thus, sodium hydroxide solutions must be standardized before any analytical use.
For standardizing NaOH, we can use various primary standards such as potassium hydrogen phthalate (PHP), succinic acid, benzoic acid, sulfamic acid, etc.
In this experiment, a standard solution of succinic acid is used as a primary standard to determine the exact concentration of sodium hydroxide. Succinic acid, which dissolves in water to form H+ and succinate ions, is a pure and stable substance that contains two titrable acidic hydrogens.
In this reaction, we use phenolphthalein as an indicator that changes color from colorless to faint pink at the endpoint/equivalence point.
Preparation of 0.1 M NaOH solution:
To make 0.1 M NaOH solution, weigh accurately 02.00 gm of NaOH and dissolve in 200 ml of distilled water in a volumetric flask, and properly mix it. Once it has completely dissolved, make up the volume to 500 ml.
Preparation of 0.1 M standard succinic acid solution:
To make 0.1 M standard succinic acid solution, weigh accurately 0.59 gm of succinic acid and dissolve in 70 ml of distilled water in a volumetric flask, and properly mix it. Once it has completely dissolved, make up the volume to 100 ml.
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 succinic acid solution and pour it into a 250 ml conical flask.
- Add 2-4 drops of phenolphthalein indicator and mixed thoroughly the mixture.
- Titrate this solution with NaOH solution until the endpoint is reached.
- The actual endpoint is indicated by the appearance of a faint pink color.
- To get accurate results, repeat the titration three times.
- Properly record the readings of the burette.
- Take their mean and calculate the molarity of sodium hydroxide solution.
Observation table:
|
Sr. No. |
Content in
conical flask |
Burette reading |
Volume of
titrant used (ml) |
|
|
Initial |
Final |
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|
1 |
|
|
|
|
|
2 |
|
|
|
|
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3 |
|
|
|
|
|
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Mean: |
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Calculations:
Calculate the solution's molarity using given formula.
NNaOH x VNaOH = N(succ. acid.) x V(succ.acid.)
Volume of succinic acid solution in each titration = 10 m
Normality of succinic acid = 0.1 M
Result:
The strength of the prepared sodium hydroxide (NaOH), solution was found to be_____M.
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