Learn about the preparation and standardization of 0.1 N HCl through a laboratory experiment or practical.
Aim:
To prepare and standardize 0.1 N HCl using sodium carbonate as primary standard (Acid-base titration).
Requirements:
Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.
Chemicals: Concentrated Hydrochloric acid (HCl), sodium carbonate, (Na2CO3), and methyl orange indicator, etc.
Principle:
A methyl orange indicator can be used to titrate the hydrochloric acid solution against the sodium carbonate solution. When a weak base is used to titrate a slightly acidic solution, the endpoint is also slightly acidic. Since the salt formed is partially hydrolyzed, the solution is slightly alkaline when a weak acid is titrated with a strong base.
The following is a reaction of sodium carbonate with hydrochloric acid.
Na2CO3(aq) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l)
CO32-(aq) + 2H+(aq) → CO2(g) +
H2O(l)
The amount of acid in an acid-base titration becomes chemically equivalent to the amount of base present. When a strong acid and a strong base are titrated together, the solution becomes neutral.
How to prepare 0.1 N HCl:
Dilute 08.50 ml of hydrochloric acid with distilled water to produce 1000 ml.
How to prepare 0.1M Na2CO3 solution:
Take 01.06 gm of sodium carbonate and dissolve in 50 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.
- Using a pipette, 05.00 ml of prepared solution of sodium carbonate and pour into a conical flask.
- Then, to this solution, add one or two drops of methyl orange indicator.
- Start the titration by adding HCl drop by drop followed by stirring continuously, until the solution turns pale pink.
- Boil the solution until the color turns yellow again, then cool and titrate again until a faint pink color is no longer affected by boiling.
- To get accurate results, repeat the titration three times.
- Properly record the readings of the burette.
- Take their mean and calculate the normality of the HCl solution.
Observation table:-
|
Sr.
No. |
Content
in conical flask |
Burette
reading |
Volume
of titrant used (ml) |
|
|
Initial |
Final |
|||
|
1 |
|
|
|
|
|
2 |
|
|
|
|
|
3 |
|
|
|
|
|
|
Mean: |
|||
Calculations:
N x V = wt. / eq. wt. x 1000
Where,
N is the normality of HCl to be calculated
V is the volume of HCl used
Wt. is weight of Na2CO3
eq. wt is equivalent Weight of Na2CO3
Result:
The strength of the prepared HCl solution was found to be_____N.
Frequently Asked Questions (FAQ):
Which solution is used for the standardization of the 0.1 N HCl solution?
As the primary standard solution, sodium carbonate is used for the standardization of 0.1 N HCl solution.
What is the molecular weight of sodium carbonate?
Sodium carbonate is the inorganic compound with the formula Na2CO3 and its molar mass is 105.9888 g/mol.
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