Little help please with a titration reaction

[CSte88]

Why is this reaction carried out in an acidic solution?

 

MnO₄^- + 8H⁺ + 5Fe²⁺ àMn²⁺ + 5Fe³⁺ + 4H₂O

 

 

Really appericate any help on this one, and sorry if its in the wrong place.

 

 

[Greg Boyles]

Why is this reaction carried out in an acidic solution?

 

MnO₄^- + 8H⁺ + 5Fe²⁺ àMn²⁺ + 5Fe³⁺ + 4H₂O

 

 

Really appericate any help on this one, and sorry if its in the wrong place.

 

 

 

 

MnO₄^- + 8 H⁺ +5 e^- Mn²⁺ + 4 H₂O 1.51 is an oxidising agent and the Fe2+ is able to be oxidised is the simplest answer.

 

 

I remember the rules with E0 values in electrolysis etc when figuring out which reactions will take place at the anode and cathode, but I don't remember what the rules are with them when figuring out if a particular redox reaction will take place.

[Fuzzwood]

To be honest, the answer is in your own question.

[spin-1/2-nuclei]

Hello,

 

First some background on this kind of titration:

 

In Redox reactions you have an oxidizing agent and a reducing agent.

 

Oxidation = loss of an electron(s)

Reduction = gain in electron(s)

 

Therefore the oxidizing agent will be the one that accepts the electrons & the reducing agent loses them.

These reactions (oxidation & reduction) take place at the same time.

 

Some important things to note:

There must be a considerably difference between the strength of the oxidizing agent and the strength of the reducing agent for good results. You use the standard reduction potential SRP to predict what will be oxidized and what will be reduced in a redox reaction. The SRP basically measures the ability of reagents to gain or lose electrons. The more positive the SRP the more it likes electrons the > the potential is to be reduced.

 

Now to help you answer your question:

The strength of the oxidizing agent is heavily dependent on the PH of the solution. So, the more acidic or basic the solution is the stronger the oxidizing agent. Accordingly, as the PH of the solution approaches neutral the ability of the oxidizing agent decreases significantly. Also remember that permanganate is self indicating and cannot be used as a primary standard: note that this is due to the impurities found in permanganate solution and the fact that it is so good at what it does. Thus it is a secondary standard that must be titrated against a primary standard.

So, to answer your question:

 

a.) Redox reactions work better in acidic or basic medium and their strength tends to decrease in neutral environments. Moreover, permanganate works in all three, but in the particular case of permanganate (it works best under acidic conditions) - I will explain why below.

 

b.) The aqueous solutions of permanganate are typically not stable for long. In addition, the permanganate typically comes contaminated with trace amounts of manganese dioxide (catalyzes spontaneous decomp of permanganate) and organic matter. When these organic substances react (catalyzed by light) with permanganate, MnO2 crashes out of solution. The permanganate also decomposes when exposed to manangous ions, however, that reaction is slower in acidic medium.

 

Hope this helps

Cheers

Edited August 18, 2011 by spin-1/2-nuclei