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

Estimation of Iron (II) and Iron (III) concentration

Extracts from this document...


The Estimation of Iron(II) and Iron(III) in a Mixture Containing Both Introduction - theory behind two methods and why I am choosing one of them There are several possible methods that could be employed to determine the concentration of Iron(II) and Iron(III) ions in solution: one of these is colorimetry. Colorimetry is the technique of using the depth of colour of a substance to measure its concentration. We use a colorimeter (see fig. 1 and 2) to measure the depth of colour. The machine is calibrated by checking a series of different known concentrations of solution; from the readings we construct a graph of absorbance (the percentage of light absorbed by the sample) against concentration - this is known as a calibration curve. We can then read off the graph the concentration value that goes with the absorbance value for our unknown solution. Figure 1: A colorimetry set up Figure 2: A colorimeter The machine may be set by the wavelength of the light involved. ...read more.


Another possible method would be a redox (reduction-oxidation) titration. Acidified potassium manganate(VII) is a popular standard solution for use in redox titrations and has the added benefit that it oxidises Fe2+ to Fe3+: MnO4-(aq) + 5Fe2+(aq) + 8H+(aq) --> Mn2+(aq) + 5Fe3+(aq) + 4H2O(l) The solution needs to be well acidified to provide the H+ ions shown in the equation. 2M sulphuric acid could be used to do this. The acid also inhibits the oxidation of Fe2+ to Fe3+ by the air. Without sufficient acid alternative reactions take place and the link between the MnO4- and Fe2+ will be lost. This titrant is self-indicating: a separate indicator is not needed. The manganate(VII) ion is bright violet, but it is reduced to the virtually colourless manganese(II) ion (it is actually very pale pink but looks colourless). When the iron(II) is finally used up, the manganate(VII) is no longer reduced, so the purple colour remains. ...read more.


Different metals would have different electrode potentials. More reactive metals ionise more easily and so they should leave more electrons on the metal before they reach equilibrium. In other words, the more negative the metal is, the more reactive it should be. If we could measure the potential difference between metal and solution we could use it to construct a table of reactivity from the different voltage readings. However, to measure this potential difference we would have to put a metal electrode into the solution and this would have its own electrode potential. A platinum electrode would be placed in a solution which is both 1 mol dm-3 in iron(II) ions and 1 mol dm-3 in iron(III) ions. Iron(II) has the lowest oxidation number and appears nearest the electrode: Fe3+(aq) + e- Fe2+(aq) Cyanide can be used to test if it is completely reduced. Calculations - justify each calculation Safety Table - remember concentrations Apparatus - put in table KMnO4 (0.0025M) Mixture containing unknown concentrations of Fe3+/Fe2+ ions in solution Ferrozine (0.2%) 1M Sulphuric Acid 0. ...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 Inorganic 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 Inorganic Chemistry essays

  1. Peer reviewed

    Determining the concentration of acid in a given solution

    5 star(s)

    I could make up my solution by weighing the sodium carbonate in the volumetric flask as this would mean I wouldn't have to move the solid, but it would be hard to get the exact amount as I couldn't really get to the solid once it was in, to adjust

  2. effects Concentration and Temperature on the Rate of Reaction

    Time Taken When Stirred by Hand (seconds) Time Taken When Stirred by Magnetic Stirrer (seconds) Time Taken When Left Without Stirring (seconds) 0.003 76.0 67.5 60.5 0.004 51.5 52.0 53.5 0.005 41.5 45.5 39.5 0.006 36.0 40.5 44.5 0.008 33.0 29.5 33.5 0.01 31.5 24.0 25.0 From my results a reliable trend can be seen fro the

  1. Bleaching experiment. Estimation of available chlorine in commercial bleaching solution.

    ( so that I2 will not be released from starch at the end point), the starch solution should be added at the later stage of the titration (when the solution just turns from brown to pale yellow). After the addition of starch, the mixture turns deep blue.

  2. Chem Lab report. Objective: To determine the concentration of potassium manganate(VII) solution using ...

    Before the titration, sulphuric(VI) acid was added to the ethanedioic acid. It was because manganate(VII) ion was reduced only at acidic medium. To be more accurate, manganate(VII) ion needed H+ ions for reaction. Ethanedioic acid was a weak acid which was only slightly ionized, it cannot provide enough H+ ions for the reaction.

  1. Determination of the formula of hydrated Iron (II) Sulphate crystals (FeSO4xH2O)

    sulphate crystals, FeSO4xH2O. Results of titration Original mass of FeSO4xH2O = 3.02 g Rough titration result = 23.10cm3 Titration number Amount of KMnO4 (cm3) amount 1 21.75 2 21.70 3 23.71 4 21.70 Average titration 21.72 The average was taken excluding the anomalous result.

  2. Aim To study the effect of concentration of iodide ion ...

    Volume of starch solution used The volume of starch solution used will be fixed at 5 drops throughout the experiment. Volume of iodide I- solution used The volume of iodide solution will be fixed at 10 cm3 throughout the experiment.

  1. Determination of the formula of complex ion

    / 3 = 24.9 dm3 No. of moles of EDTA used = (24.9/1000) x 0.1 = 2.49x10-3 mol No. of moles of Ni2+ used = (25.0/1000)

  2. Planning an investigation to determine the reactivity of HalogenoAlkanes

    In a substitution reaction, the halogen atom will leave as a halide, meaning the atom or group of atoms replacing the halogen atom must possess a lone-pair of electrons. The lone-pair is donated to the ?+ carbon atom, forming a new covalent bond.

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