Lab 9: Preparation of an Iron Oxalate Complex. (5 pts; 5 of 25 possible for this experiment) Read the Laboratory materials. Type a brief answer after...
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1.     When Iron (II) ammonium sulfate is dissolved in water, it dissociates into its component ions. 

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Lab 9: Preparation of an Iron Oxalate Complex. (5 pts; 5 of 25 possible for this experiment)
Read the Laboratory materials. Type a brief answer after each question, BEFORE coming to lab. If
uncertain of any answers, consult with your lab instructor well before the beginning of the lab when
it is due. Note: The Appendices can be found on Bb>content experiments.
PRE-LAB QUESTIONS
The following chemical equations correspond to the procedural steps you will perform in this
experiment (not necessarily the same number, but the same order). Write the complete balanced net
ionic equations in your laboratory notebook, properly indicating phases and charges. You may have
to look in the procedures in order to fill in some of the blanks.
1. When iron( II) ammonium sulfate is dissolved in water, it dissociates into its component
ions.
( )
( ) +
( ) +
2. When oxalic acid is added, the iron (II) ions precipitate as iron(II) oxalate dihydrate.
Feet (aq) +
(aq) +
H20 (1) -
( ) + _
_H (aq)
3. Next, potassium oxalate is added to the washed precipitate. Potassium oxalate dissociates
into its ions in solution. At high oxalate concentrations, iron (II) oxalate combines with
another oxalate ion to form a soluble complex ion that consists of two oxalate ions joined to
the iron (II) ion.
FeC204.2H20 (s) +
(aq) - _Fel
_ (aq) + _H20 (1)
4. Hydrogen peroxide is an effective oxidizing agent, accepting two electrons. It will oxidized
iron(II) to iron (III). This process strips some of the oxalate ion from the iron, so the product
is a mixture of Fest (aq), FeC204 (aq), and Fe(C204)2 (aq). Assume that the predominant
product is Fest (aq). This is a redox reaction; therefore you must balance the electrons
(charge) as well as the atoms.
Fe(C204)22- (aq) +
H202 (aq) -
(aq) + _C2042- (aq) + _OH- (aq)
5. The resulting solution is basic, causing some or all of the iron to precipitate as iron (III)
hydroxide, a reddish-brown precipitate.
(aq) +
OH (aq) -
( )

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6. The excess hydroxide ions must be neutralized with oxalic acid. The oxalic acid will also
neutralize the hydroxide ions of the iron (III) hydroxide precipitate, releasing the iron(III)
ion back into solution. Oxalic acid is chosen so that no additional anions will be present to
interfere with the formation of the complex. The excess oxalate ions convert all iron present
into a soluble complex ion with three oxalate ions attached to the iron(III) ion. _FB(0H)3(S)+_ (aCI)-*_( )+_H20( )+_( ) 7. At this point, there are 3 principal ions remaining in solution, what are they? You will need
to trace through all of your steps. (Hint: The solution was decanted after the second step, leaving only the precipitate in the beaker. The hydrogen peroxide reacted completely. The
oxalic acid was added in excess. Oxalic acid is a weak acid, so hydrogen ion is not a
principal ion here.) Answer in a complete sentence. 8. Once the final product ion has been made, one final substance will be added to the solution.
What is the substance and what is its purpose? 9. The solution will be green at this point due to the formation of the complex Fe(CzO4)33' ions.
When a positive counter ion, a cation, combines with these, crystals form. (aq) + (aq) + H20 (1) —r KsFe(C204)3'3H20 (s)

Top Answer

Yes ammonium iron(II) sulfate dissolves in water and... View the full answer

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