[Professor 0110]

Hey everyone,

I was just wondering if any you chemistry gurus could help me with balancing a particular chemical equation. I've tried but cannot seem to figure it out.

Here is the equation:

FeCl3 + H2S + FeCl2 + HCl + S

The hydrogen atoms are out of whack so I modified the equation thus:

FeCl3 + H2S + FeCl2 + 2HCl + S

This now leaves four Cl atoms on one side and three on the other. Multiplying the entire equation doesn't seem to work and neither does multiplying by four.

Any help in resolving this equation will be much appreciated!

Thanks!

[RobertT]

Well I don't understand how you could get 5 Reactants....
So I'm assuming the reactants are FeCl₃ and H₂S

2FeCl₃+ 3H₂S --> Fe₂S₃ + 6HCL

Just add in states..

[Borek]

FeCl3 + H2S + FeCl2 + HCl + S

This is not even a skeletal equation - reactants and products are not separated. You have to replace one plus with an arrow...

[Professor 0110]

Whoops, thanks for pointing that out Borek!

Here is the corrected equation:

FeCl3 + H2S --> FeCl2 + 2HCl + S

2FeCl3+ 3H2S --> Fe2S3 + 6HCL

 Ah, thanks Robert! But is that the actual corrected equation? Aren't the ionic parts supposed to stay together? In this case it is Iron Chloride (FeCl2).

[vhpk]

Whoops, thanks for pointing that out Borek!

Here is the corrected equation:

FeCl3 + H2S --> FeCl2 + 2HCl + S

2FeCl3+ 3H2S --> Fe2S3 + 6HCL

 Ah, thanks Robert! But is that the actual corrected equation? Aren't the ionic parts supposed to stay together? In this case it is Iron Chloride (FeCl2).

You see here FeCl₃ is an oxidizing agent and H₂S is a reducing agent. So what will happen in your opinion ?

[AWK]

Only this reaction proceeds in the solution without any base
FeCl₃ + H₂S --> FeCl₂ + 2HCl + S
When the base, eg ammonia is present, both sulfides FeS and Fe₂S₃ precipitate.

[JimClark]

If you are balancing an equation, the general principle is just to work across the equation, checking one thing at a time, but leaving anything which occurs in several places on the same side of the equation until the end.  That's the Cl in this case.

So in the original equation:  FeCl₃ + H₂S  --> FeCl₂ + HCl + S

and ignoring the chlorine for the time being, the only thing wrong is the hydrogen.  Put that right:

FeCl₃ + H₂S --> FeCl₂ + 2HCl + S

That wrecks the chlorines of course.

In most simple equations it is fairly obvious where to go next, but that's not true in this instance.  In that case, try a bit of trial and error.  There is no way this can work with the FeCl₃ as it stands - so see what happens if you have two of them:

2FeCl₃ + H₂S --> FeCl₂ + 2HCl + S

Now correct the irons on the right hand side by having 2FeCl₂.  Check the chlorines (and everything else just to be sure).  How does that look?

2FeCl₃ + H₂S --> 2FeCl₂ + 2HCl + S

Balancing equations by trial and error isn't a very good way of doing them.  For redox reactions like this one (ones involving reduction and oxidation), there are better ways which will let you balance seriously difficult equations which would make this one look very easy!  But this needs you to have a good understanding of oxidation and reduction, and a knowledge of half-equations.  If you are interested, you could explore the Chemguide menu at http://www.chemguide.co.uk/inorganic/redoxmenu.html , but if this is beyond the level you are working at, forget it for now.

[Donaldson Tan]

Actually, this is a redox problem whereby Fe³⁺ is reduced to Fe²⁺ while H₂S is the reducing agent. I hope this helps. Chloride is in fact a spectator ion in the reaction.

Attempting to balance the 2 equations below should give you the answer.

Fe³⁺ + e -> Fe²⁺
H₂S -> S + 2H⁺ + 2e