Redox Titration: Permanganate against Oxalate (Ethanedioate)

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Redox Titration: Permanganate against Oxalate (Ethanedioate)

Aims: Find out the concentration of oxalic acid and oxalate by titration with sodium hydroxide.

Chemical: Mixture of oxalic acid and oxalate, standard NaOH(about 0.05M), standard KMnO4(about 0.02M),

2M H2SO4, phenolphthalein indicator

Apparatus: Titration apparatus, Bunsen burner

Procedure:

(A) Dilution

The mixture of oxalic acid and oxalate should be diluted ten times. Using pipette filler pipette 25cm3 of given solution and dilute it to 250cm3 in a volumetric flask. The resulting solution can be used for subsequent titration.

(B) Acid-base titration

Titrate a 25cm3 portion of the diluted mixture against the given standard Sodium Hydroxide (0.05M). Add 3 drops of Phenolphthalein indicator. At the end point, the solution will change from colorless to pink. Repeat the titration for 3 more times to find out the average volume.

(C) Redox titration

Titrate another 25cm3 portion of the diluted mixture against the given standard potassium permanganate KMnO4 (0.02M). For each titration, you should add about 20cm3 2M sulphuric acid and heat the mixture to above 343K before adding the potassium permanganate. Further heating is necessary during the