Know About the Oxalic Acid Titration Using KMnO4

The titration of potassium permanganate with oxalic acid is one of the titration experiments featured in the CBSE chemistry practical curriculum. We will be going into the intricacies of the whole Low Temperature Oxidation of Oxalic Acid with KMnO4 experiment throughout this article below.

•  Objective

The potency of potassium permanganate was measured by titrating it against 0.1M oxalic acid as a standard solution.

• Hypothesis

According to the theory, when sulfuric acid and potassium permanganate are combined, sulfuric acid transforms into a potent oxidising agent with a lengthy half-life. According to the following equation, KMnO4 has an oxidising capacity of 1 in an acidic environment.

In an acidic solution, a base exists.

A reaction of MnO4– + (minus plus) 8H+ + (plus plus)5e– (minus) Mn2+ + (plus plus)4H2O has been observed.

 When permanganate solution gets introduced to a solution of a reducing agent, it discolours. This is because the solution containing MnO4– (minus) ions is purple, whereas the solution containing Mn2+ (plus) ions is colourless. 

When the concentration of potassium permanganate exceeds a specific value, the solution develops a darker shade of purple. KMnO4 acts as a self-indicator in acidic solutions, showing its presence.

Potassium permanganate’s potency is determined using pure oxalic acid as a standard. This process includes the production of redox compounds. KMnO4 oxidises oxalic acid to carbon dioxide, which KMnSO4 then reduces to create KMnSO4. The reaction between potassium permanganate and oxalic acid is as follows.

Reduction ½ reaction – KMnO4 + 3H2SO4 K2SO4 + 2MnSO4 + 3H2O + 5[O]

Oxidation ½ reaction – 5(COOH)2 + 5[O] 5H2O + 10CO2

The overall reaction that occurs during the procedure is — 2KMnO4 + 3H2SO4 + 5(COOH)2 (towards) K2SO4 + 2MnSO4 + 8H2O + 10CO (upwards)

The process’s ionic equation, shown below:

Reduction ½ reaction – [MnO4– + 8H+ + 5e– Mn2+ + 4H2O] 2 x

Oxidation ½ reaction – [C2O42- 2CO2 + 2e–] 5 x

2MnO4– + 16H+ + 5C2O42– (towards) 2Mn2+ + 10CO2 + 8H2O (Overall Iconic reaction)

 This titration can never be demonstrated with the help of nitric acid or hydrochloric acid since nitric acid or hydrochloric acid is an oxidation reaction. As a result of the chemical reaction Low-Temperature Oxidation of Oxalic Acid with KMnO4 solutions, chlorine gets formed, which seems to be an oxidising agent.

Supplies Required:

·         Acid oxalic

·         Solution of potassium permanganate

·         Sulfuric acid, 1.0M

·         Chemical equilibrium

·         Burette and Burette holder

·         Pipette

·         Flask conical

·         Funnel

·         Flask for measuring

·         Bottle for weighing

·         White ceramic tile

·         Burnet

·         Gauze made of wire

Setup of the apparatus:

·         In burette – KMnO4 solution

·         In a conical flask, add ten millilitres of oxalic acid and ten millilitres of sulfuric acid (KMnO4)

·         End Point – Achievement of a persistent light pink hue.

Methodology:

(a) Make an oxalic acid 0.1N standard solution by performing the following steps:

This equation gets used to calculate the quantity of oxalic acid required for a 250ml solution with normality of 0.1N.

The molecular weight of oxalic acid divided by the number of electrons lost by one molecule equals the equivalent weight.

o   The comparable weight of oxalic acid is 126/2 = 63 grams.

o   Strength is equal to normalcy multiplied by the comparable weight.

o   1/10 x 63 = 6.3 g/l strength (in grams per litre).

o   One litre of N/10 oxalic acid solution requires oxalic acid. The amount of oxalic acid needed is 6.3 grams.

1.      Weigh an empty watch glass with a chemical balance to measure how much it weighs.

2.      Fill the watch glass halfway with 6.3g of oxalic acid and weigh it carefully.

3.      Fill the measuring flask with oxalic acid using a funnel until it is fully saturated.

4.      Remove the funnel from the flask and wash it with distilled water while it is still in place.

5.      Pour enough distilled water to bring the solution to the desired temperature, ensuring that the oxalic acid gets thoroughly dissolved.

6.      In this solution, an oxalic acid standard solution of 0.1N get employed.

(b) The following steps are used to conduct a titration of potassium permanganate solution against a standard oxalic acid solution:

1.      Rinse the burette with the potassium permanganate solution and then fill it with the potassium permanganate solution.

2.      Secure the burette in the burette stand, then lay the white tile underneath it to correctly calculate the endpoint.

3.      10ml of 0.1N standard oxalic acid solution should get pipetted into a conical flask and refrigerated.

4.      Sulfuric acid should be added to the test tube to prevent manganese from oxidising and forming manganese dioxide.

5.      Raise the temperature of the liquid to 60 degrees Celsius before adding the potassium permanganate.

6.      Before commencing the titration procedure, make a mental note of the first burette reading.

7. Titrate the heated solution against a potassium permanganate solution while gently swirling the answer in the flask to complete the reaction.

8.      At the start of the operation, oxalic acid is employed to remove the purple colour of KMnO4. The appearance of a permanent pink colour shows that the procedure is complete.

9.      Titration repeats until concordant findings get obtained.

10.  On burette readings, the upper meniscus should be observed. Take note of the reading, insert it in the observation table, and calculate the concentration of KMnO4 in the solution.

Computation:

The following formula has applied the strength of a given KMnO4 in terms of molarity.

·         a1M1V1 = (equal to) a2M2V2 (Where a1 and a2 are the stoichiometric coefficients of oxalic acid & KMnO4 in a balanced chemical equation.)

·         a1 = 2, a2 = 5

Where,

o   M2 and M1 are the molarities of the potassium permanganate & oxalic acid solutions used in the titration.

o   V2 and V1 are the volumes of potassium permanganate and oxalic acid solutions used in the titration.

Consequently,

·         Oxalic acid = KMnO4.

·         5M2V2 = 2M1V1

·         M2 = (2M1V1/5M2V2)

The molarity is used to calculate the power of KMnO4.

Resilience = Molarity x Molar Mass

Preventative measures:

• Before beginning the study, thoroughly clean all equipment with distilled water and fill it with the solution to be utilised.
• To minimise cross-contamination, pipettes and burettes should be carefully washed before use.
• Due to the black pigmentation of potassium permanganate, carefully read the highest meniscus.
• Dilute sulfuric acid should be used to acidify potassium permanganate.
• Take accurate measurements as it approaches the exit point rather than depending on average data to decide the result.
• Use an anti-parallex or an auto-parallex card for getting burette readings.
• Avoid using rubber cork burettes since KMnO4 is capable of attacking them.
• There should be no more than two decimal places used to describe the uncertain answer’s strength.

Conclusion

Observe and document all of the essential characteristics of the Low-Temperature Oxidation of Oxalic Acid with KMnO4, as previously described. You should get acquainted with the complexities of the Titration of Oxalic acid with KMnO4 and the components that make it up to do well on the test—achieving high marks on competitive tests and exams entails memorising the nuances of the test designers’ technique.