[aerowx]

My teacher gave me this problem as an extra credit question, assuring me it would occupy my time for a while.

(Cr(N₂H₄CO)₆)₄(Cr(CN)₆)₃ + KMnO₄ + H₂SO₄ --yields-- K₂Cr₂O₇ + MnSO₄ +CO₂ + KNO₃ + K₂SO₄ + HOH

However, I solved it in under ten minutes using pencil and paper. My teacher gave up on trying to challenge me. Does anyone know of a harder equation to balance?

[Arkcon]

That's probably the worst one I've ever seen.  I almost sent you to this page:  http://www.trimen.pl/witek/calculators/wspolczynniki.html  But that's where that problem is from.

[AWK]

Its from JChemEd
H2 + Ca(CN)2 + NaAlF4 + FeSO4 + MgSiO3 + KI + H3PO4 + PbCrO4 + BrCl + CF2Cl2 + SO2 =
PbBr2 + CrCl3 + MgCO3 + KAl(OH)4 + Fe(SCN)3 + PI3 + Na2SiO3 + CaF2 + H2O

Paper, pencil and half an hour.

[Burner]

Its from JChemEd
H2 + Ca(CN)2 + NaAlF4 + FeSO4 + MgSiO3 + KI + H3PO4 + PbCrO4 + BrCl + CF2Cl2 + SO2 =
PbBr2 + CrCl3 + MgCO3 + KAl(OH)4 + Fe(SCN)3 + PI3 + Na2SiO3 + CaF2 + H2O

Paper, pencil and half an hour.

The equation is the general equation of a many-step reaction right? I have never seen chemical equations with 11 reactants and 9 products

My teacher gave me this problem as an extra credit question, assuring me it would occupy my time for a while.

(Cr(N₂H₄CO)₆)₄(Cr(CN)₆)₃ + KMnO₄ + H₂SO₄ --yields-- K₂Cr₂O₇ + MnSO₄ +CO₂ + KNO₃ + K₂SO₄ + HOH

However, I solved it in under ten minutes using pencil and paper. My teacher gave up on trying to challenge me. Does anyone know of a harder equation to balance?

Out of curiousity I searched for (Cr(N₂H₄CO)₆)₄(Cr(CN)₆)₃ on google and found that this forum has a thread on this:
http://www.chemicalforums.com/index.php?topic=76462.5

By the way, what is (Cr(N₂H₄CO)₆)₄(Cr(CN)₆)₃ exactly and how it is used other than being in a hard chemical equation for balancing? Nothing useful is found on Google, ChemSpider, PubChem, and a lot of other databases

[AWK]

The equation is the general equation of a many-step reaction right? I have never seen chemical equations with 11 reactants and 9 products

Right. Reaction should be split in ~10 steps. As a starting point I used balancing of sulfur and scaling between each step.
(Cr(N2H4CO)6)4(Cr(CN)6)3 is a complex Cr(urea)₆³⁺ and Cr(CN)₆^3-. This comes from redox challange of JChemEd also.

For my students I prepared a file on non-standard balancing difficult redox reactions (in Polish, but language of reactions is understandable for all) search Google for pdf:
trudne redoksy forum

[Borek]

These difficult reactions are just an art for arts sake. Those with oxidation of some fancy organometallic compounds are rather trivial to design, the one with 11 reactants and 9 products is sometimes called Blakley equation, as it was produced - using linear algebra - by G.R. Blakley here: http://pubs.acs.org/doi/abs/10.1021/ed059p728

It has nothing to with a real chemistry.

[AWK]

Those with oxidation of some fancy organometallic compounds are rather trivial to design, the one with 11 reactants and 9 products is sometimes called Blakley equation, as it was produced - using linear algebra - by G.R. Blakley here: http://pubs.acs.org/doi/abs/10.1021/ed059p728

Not exactly. Blakley wrote: "Only the matrix method (described below) is powerful enough to balance the skeletal chemical equation". And this statement in not true.

It has nothing to with a real chemistry.

I agree. The Blakley reaction is a kind of chemical heresy.

[Borek]

Same paper, summary:

If somebody has a list of chemical species and wants to know the collection (be it void or nonvoid) of all possible chemical reactions among them - but not involving any other chemical species as either reactants or products - the matrix method quickly (less than one second run time of an already compiled FORTRAN program on a large mainframe) and cheaply (a few 1982 dimes) gives the complete answer.

I read it as meaning the equation was generated using brute force on a database of compound formulas.

Actually matrix method is not working for some reactions, but that's another story.

[Babcock_Hall]

@OP, Maybe it is time to turn your attention to other kinds of chemical problems.