Acid Base Titration

Titration of oxalic acid solution against sodium hydroxide

In this acid-base titration, oxalic acid is completely neutralized by the base (NaOH) according to the following reaction:

According to this reaction, two moles of sodium hydroxide neutralizes one mole of the acid for complete neutralization. The end point is indicated by phenolphthalein indicator. It is colourless in acid medium and pink in the basic medium.

Using the empirical relation, you can calculate the strength of sodium hydroxide.

a₁ M₁ V₁ = a₂ M₂ V₂

Experiment: To find out the Molarity of given NaOH solution by titrating against M/10 solution of oxalic acid.

How To Perform Experiment

Apparatus Required

Burette, pipette, clamp stand, white tile or paper, conical flask, wash bottle, beaker.

Chemicals Required

M/10 oxalic acid solution, phenophthalein, sodium hydroxide solution

Procedure

Take a clean burette, rinse it with the given sodium hydroxide solution and clamp it vertically in a burette stand. Fill the burette with sodium hydroxide solution.

Ensure that no air bubbles are there in the stop cock. Note the initial reading (V₁).

Rinse a clean 20 mL pipette with M/10 oxalic acid solution and then pipette out 20 mL of the given standard oxalic acid solution into a clean conical flask.

Add a few drops phenolphthalein indicator. Hold the conical flask just below the nozzle of the burette and using your left hand, release sodium hydroxide solution into the conical flask drop by drop.

Continuously swirl the contents of the conical flask smoothly and continue addition of NaOH solution drop wise till the appearance of pink colour.

Note down the reading of the lower meniscus of NaOH solution. This is the final reading (V₂).

Repeat the titrations to get at least three concordant readings.

End Point

Colourless to pink colour