Tuesday, August 16, 2022

Standardization of NaOH with oxalic acid

Learn about the preparation and standardization of Sodium hydroxide through a laboratory experiment or practical.

Aim:

To prepare and standardize sodium hydroxide standard solution with oxalic acid by acid–base titration.

Requirements:

Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, wash bottle, etc.

Chemicals: LR grade oxalic acid (C2H2O4), sodium hydroxide (NaOH), phenolphthalein indicator, etc.

Apparatus: Digital/analytical balance

Principle:

It is an acid-base titration in which sodium hydroxide is a strong base and oxalic acid is a weak acid. When oxalic acid reacts with sodium hydroxide, sodium oxalate and water are formed. The phenolphthalein (HPh) indicator is used to determine the endpoint of this titration. The endpoint is when the color changes to pale pink and persists for 30 sec.

Standardization of NaOH with oxalic acid

Because oxalic acid compliance with all primary standard requirements (Properties), it is use as a primary standard and can later be used to standardize other solutions.

Preparation of 0.1M NaOH solution:

Weigh accurately 04.00 gm of sodium hydroxide and dissolve in 500 ml of distilled water in a volumetric flask, and properly mix it. Once it has completely dissolved, make up the volume to 1000 ml.

Preparation of oxalic acid solution:

Weigh accurately 0.63 gm of oxalic acid 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 with distilled water.

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 20.00 ml of prepared oxalic acid solution and pour it into a conical flask.
  • Add 2-3 drops of phenolphthalein indicator.
  • Titrate the sample solution with the sodium hydroxide (NaOH) solution until the pink color appears.
  • Properly record the readings of the burette.
  • To get accurate results, repeat the titration three times.

Observation table:


Sr. No.

Content in conical flask

Burette reading

Volume of titrant used (ml)

Initial

Final

1

 

 

 

 

2

 

 

 

3

 

 

 

 

Mean:


Calculations:


The following equation can be used to determine the molarity of a NaOH solution.

N 1V 1=N 2V 2

N 2 = N 1V 1/ V 2

Result:


The strength of the prepared NaOH solution was found to be_____M.


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