How to convert Fe2O3 to Fe2+?

[brendon_504]

How to convert Fe2O3 to Fe2+?
I'm a bit stuck.

[Hellrocks]

Fe2O3 + 6H+ + 2e=> 2Fe2+ + 3H2O

[brendon_504]

But what solution/s could I add to make this reaction to happen?

[Hellrocks]

Just needs acid e.g. H2SO4 as you can see on LHS of equation

[brendon_504]

Thanks!

[Hellrocks]

Sorry had to add that you need also a strong reductant.

[charmanderp]

The fact that the product has a charge on it immediately suggest that this is either going to need a redox reaction. First step is to calculate the oxidation number of Fe on either side. On the right hand side it is clearly +2, and on the left it is +3. This decrease in oxidation number means that Fe is being reduced (we can deduce this also by the fact that it's losing oxygen).

So therefore we will need a reductant. A common reducing agent mentioned in VCE is sodium oxalate. If were were to balance both the reduction and oxidation halves and then put them together we'd noticed H+(aq), which means that we need to add a catalyst in the form of an acid (to donate protons to solution) in order to catalyse the reaction. So as well as the redutant, we need to add a reactant such as H2SO4.

[brendon_504]

Could you make a balanced equation for me...you lost me halfway :/

[charmanderp]

That bit's not really important. Just know that Fe is reduced from Fe2O3 to Fe2+. So therefore, in a redox reaction, it needs to react with a reductant. In most redox reactions we need an acidic catalyst to provide the protons necessary to hasten the reaction.

The balanced reaction though would be: Fe2O3(aq) + 6H+(aq) + 2e- > 2Fe2+(aq) + 3H20(l).

As we can see, there are H+ protons attached to the water molecules (shorthand for H3O+). Where do they come from? The acidic catalyst.

[Hellrocks]

Please explain:
How is it a catalyst? (refer back to the definition of a catalyst)

[charmanderp]

Ok. A catalyst is a substance which increases the rate of a reaction. Lets look at condensation. If we simply combine an alcohol and a carboxylic acid, it would take a few thousand years to actually form an ester (iirc). If we add a proton donating substance (like an acid), a H+ will latch itself on the alcohol, making it easy for the negatively charged OH- from the carboxyl group to attack the alcohol and form the ester link.

Similarly, a redox reaction can only occur quickly in an acidic environment. In order to produce that, we need to add H+, which is most easily done by adding an acid which easily ionises in water (essentially a strong acid).

I'm sorry, this is a really poor explanation ):

[Hellrocks]

But where has the H+ gone in this case?
A true catalyst does not get consumed in the reaction