Answer to Question #180502 in Inorganic Chemistry for Cyra Fatima

Question

The formula for hydrated iron(II) sulfate is FeSO4.xH2O.The value of x is a whole number between 1 and 10. It can be determined by carrying out a titration with 0.0200 mol/dm3potassium manganate(VII) (KMnO4) solution as follows:• dissolve a sample of FeSO4.xH2O in water to make 250 cm3 of solution • measure out 25.0 cm3 of this solution into a conical flask • add the KMnO4 solution using a burette until the end point is reached• record the volume of solution added • repeat the titration three more times .The table shows the results. Concordant results are those within 0.20 cm3 of each other. Select concordant results from the table. *

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Answer 1

10FeSO₄ + 2KMnO₄ + 8H₂SO₄ = 5Fe₂(SO₄)₃ + K₂SO₄ + 2MnSO₄ + 8H₂O

You need the number of moles of FeSO₄xnH2O, which is equal to the number of moles of FeSO₄. You need to determine the volume of KMnO₄ needed to react with the solution (the equivalence point is reached when the purple colour won't disappear anymore, as there are no Fe²⁺ ions left to oxidize). Now you can calculate the number of moles of KMnO4 and then using the equation you can find out the amount of FeSO₄ in the solution. As you have diluted the original solution you have to do some additional calculations to determine the amount of Fe²⁺ ions you started with.

The main formula to use is concentration (mol/dm³) = number of moles (mol) / volume (dm³)