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Homework Help: I Really Need Help! Chemistry: Synthesis of a Coordination Compound!

  1. Mar 22, 2010 #1
    1. The problem statement, all variables and given/known data

    Mass of Ferrous Ammonium Sulfate (limiting reagent) = 4.00 grams.

    Mass of K3[Fe(C2O4)3].3H2O = 2.54 grams.


    1. Using the above mass of ferrous ammonium sulfate calculate the theoretical yield of the K3[Fe(C2O4)3].3H2O
    2. What is the percent (%) yield of the K3[Fe(C2O4)3].3H2O
    3. Draw the shape of the complex ion {I have this one already...thanks! :)}
    4. What is the oxidation state of teh central metal ion?
    5. What is the coordination number of the central metal ion?

    2. Relevant equations

    (1) FeSO4.(NH4)2SO4.6H2O + H2C2O4.2H2O --> FeC2O4 + (NH4)2SO4 + H2SO4 + 8H2O

    (2) 6FeC2O4 + 3H2O2 + 6K2C2O4.H20 --> 4K3[Fe(C2O4)3].3H20 + 2Fe(OH)3
    + 6H20

    (3) 2Fe(OH)3 + 3H2C2O4.2H2O + 3K2C2O4.H2O --> 2K3[Fe(C2O4)3].3H2O + 9H2O

    3. The attempt at a solution

    O.k...I really have NO idea how to do this but here is what I think...
    I understand that it's about stoichiometry, recognizing which reactant is the limiting reagent
    and then calculating the moles of that reactant and then developing molar ratios. Then, when I have calculated my theoretical yield I could divide my actual yield by it and then multiply by 100 and get my percent yield. The problem is that the equations look long and complex and I'm intimidated. Also, I would have no clue as to the remaining questions. This assignment is worth a lot for me so any help anyone could offer me would be TRULY and GREATLY appreciated, thanks!!!!! :)
    Last edited: Mar 22, 2010
  2. jcsd
  3. Mar 23, 2010 #2


    User Avatar

    Staff: Mentor

    You are close. You don't have to recognize limiting reactant - you are already told which one it is. Try to approach it just looking at the number of moles of important reactants - that is, you start with x moles of Fe, how many moles of the final product can you produce? It is enough to count Fe atoms to get the idea.

  4. Mar 23, 2010 #3

    Thank you for your reply. Here is my attempt...

    So... ferrous ammonium sulfate = FAS & potassium trioxalatoferrate = PTOF

    (1) 4.00 g FAS x (1 mol FAS / 392.14088 g ) = 0.010200415 mol of FAS.

    0.010200415 mol FAS x (1 mol PTOF / 1 mol FAS) = 0.010200415 mol of PTOF

    0.010200415 mol PTOF x (491.24274 g / 1 mol PTOF) = 5.01 g PTOF {theoretical yield}

    (2) (2.54 g PTOF / 5.01 g PTOF) x 100 = 50.7 % {percent yiel}

    (3) Got it.

    (4) The central metal ion I believe would be iron (Fe) and it's oxidation state I think it would be +3?

    (5) I'm not entirely sure as to what a coordination number is but as far as I know it's the number of atoms the atom in question is bonded to...? In this case I think it would be 6???

    So far, is this correct? Thank for your time!
    Last edited: Mar 23, 2010
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