Concentration of oxalic acid Paper
The redox titration will be done between potassium permanganate and ethanedioic acid. This reaction requires acid catalyst because ethanedioic acid is too weak an acid to make the solution acidic enough to react at a reasonable rate. Sulphuric acid is in the mixture and provides the acid catalyst. The ethanedioic acid in the mixture will reduce the manganate(VII) ions (MnO4-) into manganese(II) ions (Mn2+). The potassium permanganate will oxidise the oxalic acid into carbon dioxide. H2C2O4(aq) + MnO4-(aq) CO2(g) + Mn2+(aq) Reactants Products H2C2O4: Carbon +3 CO2: Carbon +4 MnO4-: Manganese +7 Mn2+: Manganese +2.
To work out the ionic equation, balanced electron-half equations for both the potassium permanganate and the ethanedioic acid have to be worked out. Adding electrons (e-), water (H2O) and hydrogen/hydroxide ions (H+/OH-) depending on the conditions, they can be created. Manganate(VII) ions are reduced to form manganese(II) ions. MnO4- + 8H+ + 5e- ? Mn2+ + 4H2O Ethanedioic acid is oxidised to form carbon dioxide. H2C2O4 ? 2CO2 + 2H+ + 2e- The two equations combine and are balanced to create the overall ionic equation. 2MnO4- + 6H+ + 5H2C2O4 2Mn2+ + 8H2O + 10CO2.
1) Use the pipette and the pipette filler to collect 25ml of the mixture of oxalic acid and sulphuric acid and put it in the conical flask. 2) Use the clamp to connect the burette with the retort stand. 3) Use the funnel to fill the burette with the potassium permanganate until the meniscus reaches zero. 4) Place the conical flask with the mixture underneath the point of the burette.
5) Using the stopcock on the burette, enter the potassium permanganate into the conical flask until there is a colour change to produce a rough estimate. Record this in a table in cm3. 6) Carry out the same experiment again slowly to record a more accurate answer. Record in the table. 7) Repeat step 7) until two concordant results have been collected.