Redox titration is the type of titration based on redox reaction between the analyte and titrant. Redox titration includes oxidation half reactions and reduction half reactions. Oxidation reduction reactions involve transfer of electrons. In this experiment, both oxidation half reactions and reduction half reactions are found. The purpose of the experiment was to observe the redox titration of potassium permanganate and sodium oxalate in an acidic solution and to determine the average molarity of the potassium permanganate by titrating sodium oxalate solution of known molarity. It was hypothesized that the potassium permanganate neutralized sodium oxalate completely and molarity of potassium permanganate could be determined by titration.
For this experiment, burette, beaker, graduated cylinder, stirrer, dropper, funnel, sodium oxalate and potassium permanganate were used. At first the burette was filled with potassium permanganate up to zero level. Approximately 0 g of sodium oxalate was measured and kept inside the beaker to make aqueous solution of sodium oxalate. Again about 3 mL of 3M sulfuric acid was measured in graduated cylinder and mixed with the solution of sodium oxalate to make acidic solution. The whole solution was placed above stirrer to mix the solution completely. The burette filled with potassium permanganate was placed above solution so that potassium permanganate could drop to the solution. At each titration, single drop of potassium permanganate was added at a time to the solution of beaker. At first addition of potassium permanganate to the solution, the solution was left for a while to react completely with acidic sodium oxalate solution until the pink color changed to purplish color. After some time, another
drop of potassium permanganate from burette was dissolve in the solution. After 5 mL of potassium permanganate, the titration was done a little fast than previous. The potassium permanganate was added to the solution until the solution stayed purple. The same experiment was repeated for 4 times with different measurements of sodium oxalate and molarity was calculated at each experiment through titration. After completion of the experiment, the burette was rinsed with water and solution was disposed to the waste. The burette was neutralized by the acidic solution of sodium oxalate and then was cleaned with water.
The molarity of the potassium permanganate was calculated at each time through titration with acidic solution of acidic oxalate. The data was collected for each experiment and data were included in the table.
Trial Mass of sodium oxalate (g)
Volume of H 2 SO 4 (mL)
Volume of KMnO 4 (mL) 1 0 3 43 mL 2 0 3 36 mL 3 0 3 40 mL 4 0 3 40 mL
Oxidation- half reactions: MnO 4 - + 8H+ + 5e-→ Mn2+ + 4H 2 O ] ×
Reduction- half reaction: (COO-) 2 – 2e-→ 2CO 2 ] ×
Redox reaction: 2MnO 4 - + 16H++ 5(COO-) 2 - → 2Mn2+ + 8H 2 O + 10CO 2
2KMnO 4 - + 5Na 2 C 2 O 4 + 8H 2 SO 4 → K 2 SO 4 + 2MnSO 4 + 10CO 2 + 5Na 2 SO 4 + 8H 2 O
Now, the molarity of potassium permanganate could be calculated by titration, which is given by,
36 mL KMnO 4 =0 Na 2 C 2 O 4 × 2 molNa 5 molKMnO 2 C 2 O 44 × 1 LKMnO 14 × 36 mLKMnO 1000 mL 4
For 3rd trial, the mass of sodium oxalate is 0, the moles of sodium oxalate could be obtained as given below:
Moles of sodium oxalate= molarmassof sodiumoxalatemassof sodiumoxalate
Now, the molarity of potassium permanganate could be calculated by titration, which is given by,
40 mL KMnO 4 =0 Na 2 C 2 O 4 × 2 molNa 5 molKMnO 2 C 2 O 44 × 1 LKMnO 14 × 40 mLKMnO 1000 mL 4
For 4th trial, the mass of sodium oxalate is 0, the moles of sodium oxalate could be obtained as given below:
Moles of sodium oxalate= molarmassof sodiumoxalatemassof sodiumoxalate
Now, the molarity of potassium permanganate could be calculated by titration which is given by,
40 mL KMnO 4 =0 Na 2 C 2 O 4 × 2 molNa 5 molKMnO 2 C 2 O 44 × 1 LKMnO 14 ×40 1000 mLKMnOmL 4
Hence, the average molarity of KMnO 4 could be determined which is given below,
Average molarity of KMnO 4 = 0+0+ 4 0+0.
Hence, the average molarity of potassium permanganate was found to be 0 M.
The molarity of potassium permanganate for each trial was calculated and the average molarity of potassium permanganate was found to be 0. the experiment helps to find the molarity of solution by titration. The experiment also helps to know the concept of redox reaction and titration. The possible reasons of error in the experiment due to inappropriate amount of chemicals, contaminated burette and measurements. These errors could be reduced by taking appropriate amount of chemicals and using clean vessel or burette. The experiment could be used in future to determine the molarity of other compounds through titration of redox reactions.
For this experiment, around 0 g of sodium oxalate was measured and aqueous solution of sodium oxalate was prepared. Around 3 mL of 3M sulfuric acid was added to the solution to make the solution acidic. Then, the burette filled with potassium permanganate was allowed to