Synthesis and Characterisation of Iron Oxalato Complexes K x Fe y (C2O4) z. n H 2 O Make it via two routes then find x y z and n ch?v=TkZFuKHXa7w

Potassium Ferrioxalate

Synthesis From two routes – single step from Iron (III) Chloride FeCl 3. 6H K 2 C 2 O 4  K x Fe y (C 2 O 4 ) z. n H 2 O

Synthesis 2 Two steps from Iron(II)Ammonium Sulphate Oxidising Iron (II) to Iron (III) with peroxide Fe(II)  Fe (III) Reaction of Iron (III) with Oxalate to form complex

Techniques: Recrystallisation % Yield Hot titration with KMnO 4 Gravimetric Analysis Standardising Solutions Ion Exchange

Analysis Synthesis of pure sample: Recrystallisation Yields from both methods Characterisation Permanganate titration for Oxalate Heating constant mass to get H 2 O Back titration NaOH to get Fe(III) Cation Exchange to get K

Oxalate Titration MnO C 2 O 4 2-  Mn 2+ + CO 2 Since KMnO 4 solutions are not stable over a long time period they must be standardised before use. The rate of this is very slow at room temp so titration is done at 80 C

Ion Exchange Determines Potassium and Iron Involves changing the Potassium in the complex for H+ ions RSO 3 - H+ + K + xFe(C 2 O 4 )y  RSO 3 - K+ + xH + + Fe(C 2 O 4 ) y Moles K + added = moles H + released Titrate the released H + with NaOH to get the amount of Potassium After all the acid has been neutralised in the solution, further addition of NaOH results in Fe NaOH  Fe(OH) 3 (ppt) + 3Na + The amount of NaOH required to precipitate all the Fe can be used to determine the amount of Fe in the original sample

Heating to Constant Mass The amount of water is determined by gravimetric analysis A known mass of the complex is accurately weighed, heated and reweighed until the mass does not change The weight of water is the mass difference between the hydrous and anhydrous forms of the complex

Fe(III) – Back Titration Theory – The Fe(III) is difficult to titrate directly, it is photosensitive some other reactions complicate direct measurement The Fe(III) is instead reacted with an excess of base and then the base that is left over is titrated. By considering how much base is left over you can work out how much Fe(III) was there in the first place

Fe(III) – Reduction and Titration Theory – The Fe(III) is difficult to titrate directly, it is photosensitive some other reactions complicate direct measurement The Fe(III) is instead reacted with Aluminium or sunlight to reduce it to Fe(II) and then titrated again with the KMnO 4. Fe 2+ + MnO 4 -  Fe 3+ + Mn 2+

Planning Read the 3 articles provided to get some background about Iron Oxalato Complexes and understand the synthesis of it Read the practical methods and familiarise yourself with the techniques Make sure you understand key stop points Remember your complex is photosensitive

Risk Assessment The following chemicals need to be carefully risk assessed: Iron(III)Chloride Iron(II)Ammonium Sulphate Oxalic Acid Potassium Oxalate Hydrogen Peroxide Potassium Permanganate Phosphoric Acid