Practical investigations

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I am investigating the percentage purity of iron in cast iron. I know the method of titrating it against potassium manganate but I am a bit unsure about the calculations. Please can I have some guidance?

Ulex replies Try the following steps.
 
1 Work out how many moles of manganate(VII) ions were used in an average titration.
 
2 Write the equation for the reaction. You should see from this that 1 mole of MnO₄^- reacts with 5Fe²⁺.
 
3 Work out how many moles of Fe²⁺ reacted with the number of moles of MnO₄^- which you have just calculated.
 
4 Work out from this the number of moles of Fe²⁺ in your whole sample of iron.
 
5 Multiply by 56 to get the mass of actual iron in your sample.
 
6 Divide this by the mass of cast iron used and multiply by 100 to give a percentage.

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: 11 May 2006