• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Determination of the Percentage of Oxalate in Iron(II) Oxalate by Redox Titration

Extracts from this document...


Experiment 3 Determination of the Percentage of Oxalate in Iron(II) Oxalate by Redox Titration 28-9-2005 Objective To determine the percentage by mass of oxalate in a sample of iron(II) oxalate Introduction Acidified potassium permanganate is a strong oxidizing agent. It oxidizes substances and reduces itself. MnO4- + 8H+ + 5e- -------------> Mn2+ + 4H2O (Purple) (Colourless) Both iron (II) and oxalate ions can be oxidized. When they come in contact with an oxidizing agent, the following reactions occur: 1. C2O42- ------------------> 2CO2 + 2e- 2. Fe2+ ------------------> Fe3+ + e- (Pale green) (Yellow) So, when potassium permanganate is added to acidified iron (II) oxalate, two redox reactions occur. 1. 5C2O42- + 2MnO4- + 16H+ + -------------> 2Mn2+ + 8H2O +10CO2 2. 5Fe2+ + MnO4- + 8H+-------------> Mn2+ + 4H2O + 5 Fe3+ Notice the color changes of the solution. At the beginning, the color of solution inside the conical flask should be pale green due to the iron (II) ions present. Then after a certain amount of potassium permanganate is added, it should change to yellow because iron (III) ions are formed. Finally, the color of the solution should change from yellow to purple after 1 excess drop of permanganate is added. ...read more.


Then there would be 9.122 X 10-3 moles of oxalate in 250cm3 of the solution. Weight of C2O42- in the sample = 9.122 X 10-3 X (12 X 2 + 16 X 4) = 0.803g Percentage by mass of C2O42- in the sample (found by experiment) = 0.803 / 1.782 X 100% = 45.04% Molar mass of FeC2O4 .2H2O as written on its bottle = 179.9 g/mole Percentage by mass of C2O42- in the sample (theoretically) = (24+16 X 4)/ 179.9 X 100%= 48.92% Conclusion Percentage by mass of C2O42- in the sample, as found by experiment, is 45.04%. Percentage by mass of C2O42- in theory is 48.92%. Discussion 1. There was one procedure that I mentioned in the procedures section. It was that the iron (II) oxalate needed to be heated to 60oC before it can be titrated. Why is this step necessary? It was because the redox reaction between oxalate ions and permanganate ions were too slow. Why was the redox reaction between the two ions slow? This is due to 2 reasons. First, both ions are anions. They both carry the same negative charge. So, when they come close together, they would repel each other. The second reason is because of the structure of the 2 ions. ...read more.


If heating is insufficient, it would take a long time for the purple color of the permanganate which is just added to change colour. So, a persistent colour change of the solution would not indicate the end point. 5. To make sure that exactly 25cm3 of oxalate solution is obtained, pipetting of it must be done with great care. Otherwise, if more or less of the solution is obtained, the titrations would become inaccurate. 6. It takes time to let the oxalate ions, iron (II) ions and permanganate ions to react with each other. So, the permanganate ions may not be decolourized directly. Also, at the start, the permanganate ions experience more repulsion from the oxalate ions. So, it may need more time for the permanganate ions to react with the oxalate ions. 7. Add an excess of potassium iodide and sulpuric acid into 25cm3 of potassium iodate. Pour this solution into a conical flask. Then, pour sodium thiosulphate into a burette. Titrate the solution in the conical flask with the thiosulphate. Just as the brown colour of iodine fades, add a drop of starch indicator. Find out the volume of thiosulphate required to decolourize the blue-black color of the starch solution. Then calculate the number of moles of thiosulphate ions used in the titration, and the molarity would be found. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Physical Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Physical Chemistry essays

  1. Acid-Base Titrations.

    As a consequence, Ka = 1.75 x 10-5 = [H3O+][CH3COO-]/[CH3COOH] and [H3O+] = 1.75 x 10-5, pH = 4.76. The acetic acid is three-quarters titrated when 75 mL of the NaOH solution have been added. At this point 3/4 of the original moles of CH3COOH have been titrated to CH3COO-,

  2. Investigating the rate of reaction between peroxydisulphate(VI) ions and iodide ions

    This iodine is then used in the second reaction (R2). Temperature Having a reaction at higher temperatures introduces more energy into the system. This increases the average kinetic energy of the reacting particles, which in turn increases the likelihood of collisions between reacting particles.

  1. The Determination of rate equation

    The cross will act as the indicator for the experiment, the solution will be placed on top of the cross to measure the rate of reaction, and we will time using a stop watch how long it takes for the solution to become cloudy and the cross to disappear through the solution from the birds eye view.

  2. Investigating the Volume of a Drop

    This hypothesis was disproved in the experiment. We found that the volume of a drop of bottled water at 0.5 degrees Celsius is 0.01ml less than the volume of a drop of saturated salt water at 0.5 degrees Celsius. For our experiment, we couldn't prove that temperature affected the temperature

  1. Investigating the Rate of the Reaction between Bromide and Bromate Ions in Acid Solution

    of reactant, the reaction is said to be second order with respect to that reactant. In general, if; (Equation 1.5.1) where [reactant] is the concentration of a reactant, then the reaction is nth order with respect to that reactant. Graphs can be drawn of the rate against the concentration to

  2. A Redox Titration " Determining the percentage of iron in an iron ore

    Stopper the flask and invert it several times in order to mix the contents well. i. Label the flask as 'Standard'. 3. Standardization of diluted manganate(VII) solution a. Wash a 25.0 cm3 pipette with distilled water and then with manganate(VII)

  1. Double Displacement Reactions

    No Clear 27 BaCl2 NaC2H3O2 No Clear 28 BaCl2 (NH4)2SO4 Yes White Clear 29 BaCl2 Al(NO3)3 No Clear 30 BaCl2 Pb(NO3)2 Yes White Clear 31 BaCl2 Cu(NO3)2 No Clear 32 Na2CO3 Na2CO3 No Clear 33 Na2CO3 Ca(NO3)2 Yes Blue White 34 Na2CO3 Na2PO4 No Clear 35 Na2CO3 NaBr Yes White

  2. Chemistry report - In this experiment, it is a redox titration method to standardize ...

    5.70 4.30 8.00 Volume of KMnO4 used/ cm3 26.60 26.50 26.80 26.63 Summary: 25.00 cm3 of the acidified ammonium iron(II) sulphate required 26.63 cm3 of the potassium manganate(VII) solution for reaction. Calculation: 1. Calculate the number of moles of ammonium iron(II) sulphate crystals, FeSO4 .(NH4)2SO4.6H2O in the weighed sample. No.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work