Question

Determine strength of oxalic acid by titration against kmno4 solution

Answer 1

Answer:

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Explanation:

Procedure :

(a) Preparation of 0.1N standard solution of oxalic acid:

The quantity of oxalic acid required for the 250ml of the solution having a normality of 0.1N can be calculated as follows.

Equivalent weight of oxalic acid = Molecular weight/No of electrons lost by one molecule

Equivalent weight of oxalic acid = 126/2 = 63

Strength = Normality x Equivalent weight

Strength = 1/10 x 63 = 6.3 g/l

For the preparation of 1 litre of N/10 oxalic acid solution amount of oxalic acid required = 6.3 g

Weigh an empty watch glass using a chemical balance.

Weigh 6.3g of oxalic acid accurately in the watch glass.

With the help of a funnel transfer the oxalic acid into the measuring flask.

Now wash the funnel with distilled water without removing the funnel from the flask.

Make the solution up to the marked point with distilled water and make sure the oxalic acid fully dissolved.

This solution is 0.1N standard solution of oxalic acid.

(b) Titration of potassium permanganate solution against standard oxalic acid solution:

Rinse the burette with the potassium permanganate solution and fill the burette with potassium permanganate solution.

Fix the burette in the burette stand and place the white tile below the burette in order to find the end point correctly.

Pipette out 10ml of 0.1N standard oxalic acid solution in a conical flask.

Add a test tube full of sulfuric acid in order to prevent oxidation of manganese to form manganese dioxide.

Heat the mixture upto 60oC before titrating with potassium permanganate.

Note down the initial reading in the burette before starting the titration.

The hot solution is titrated against potassium permanganate solution and simultaneously swirl the solution in the flask gently.

Initially the purple colour of KMnO4 is discharged with oxalic acid. The appearance of permanent pink colour reveals the end point.

Repeat the titration until concordant values are obtained.

Note down the upper meniscus on the burette readings. Record the reading in the observation table given below in order to calculate the molarity of KMnO4 given.

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