Practical investigations

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I am doing a practical investigation into what affects the oxidation of Fe²⁺ ions to Fe³⁺ ions in iron tablets. I want to vary temperature and pH, but I'm really stuck on how to do it. And also is it possible to find the molarity of Fe²⁺ in the tablets and then use the appropriate amount of iron(II) sulphate powder instead of using the tablets each time? I am using a titration with potassium manganate(VII).

Ulex writes
 
Taking your last question first. Why not make this part of the investigation? Carrying out the titration should enable you to calculate the number of moles of iron(II) sulphate in each tablet.
 
Now for the first question. I take it you want to investigate the extent of oxidation of iron(II) sulphate by the oxygen of the air under varying conditions. A suggestion to start you off. Prepare 4 or 5 petri dishes with 1 tablet's worth of iron(II) sulphate in each. Add to each petri dish the same volume of acid with a different pH in each (or use buffer solutions?). Leave open to the air for the same length of time. Then transfer each mixture to a volumetric flask, make up to the mark with dilute sulphuric acid and titrate each with potassium manganate(VII) to find out how much iron(II) is still present. I have no idea whether this will show significant variation but it's a start!
 
Always carry out a risk assessment and check with your teacher before starting any practical work.

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.

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updated: 12 February 2007