Estimating the Iron(II) content in an iron tablet using a standard solution of potassium manganate (VII)

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Candidate Name: Yi-Chun Teng

Candidate Number: 001407-038

Estimating the Iron(II) content in an iron tablet using a standard solution of potassium manganate (VII)

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Calculating the amount of iron(II) present

The iron was oxidized from its 2+ state to 3+ by sulfuric acid:

And the manganate iron was reduced as follows:

This half equation is balanced as follows:

Since the above equation involves the transfer of five electrons, the equation involving iron needs to be multiplied by five before the two half equations can be added together:

Adding the two half equations:

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This simplifies to:

This equation shows that for every five  present, one is required for the reaction to be completed.

19.1ml of potassium manganate solution was used for titration. From this the amount of manganate ions used can be calculated as follows:

Amount of  present =

Mass of present =

Since the volume of  solution used was 25cm3, one-tenth of the total solution made from the five iron tablets, the above calculation shows that:

. Dividing this value by 5, we get 53.3mg of Fe present in each tablet.

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