Practical investigations
Read our general notes on Risk Assessment
Hi, I am currently writing up my investigation into the reaction between oxalate ions and manganate ions, but I can't seem to find how sulphuric acid is involved in the reaction and what the rate determining step is? I would be grateful for any help!
Igloo writes ...
I can give you an answer to your first question but only a little help with the second.
You will see from the ionic equation for the reaction that a very large number of hydrogen ions are needed for the reaction to take place to form the products, Mn2+, H2O and CO2, (16H+ for every 5 C2O42- ions) and from the formula of oxalic acid, H2C2O4 you can see that only 10H+ are created for every 5C2O42- ions. This is where the sulphuric acid comes in - it provides the extra hydrogen ions required. However, although hydrogen ions are needed at some stage in the process, they may or may not be involved in the rate determining step. You will probably not find a great deal of help on the internet either, because although this reaction has been studied in some depth, researchers have tended to concentrated on the autocatalytic nature of the process. However, I have found a : web reference for you. It is at:
One thing which will immediately strike you is that this reaction is incredibly complex, involving a large number of intermediate species. You should note that the article claims on the first page or so that sulphate (and hydrogensulphate) ions are not involved in the rate determining step, though of course hydrogen ions may well be.
However, don't forget that these derive from the oxalic acid as well, and that in all your explanations you should consider the ionic species as being the reactants (MnOM4-, H+ and C2O42-) rather than the molecules (KMnO4, H2SO4, H2C2O4). Hopefully your own research might have established the order of reaction with respect to manganate(VII) ions and oxalate ions, and if you sift more carefully through this complex article than I have had the time to do, then you may well find the answers you are looking for.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
back to Practical investigations
Rate this page or react
Share your views on this page, 11 ratings so far
, rated at 
updated: 17 January 2006
