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The use of cast iron cookware with acidic foods such as fruits can result in significant amounts of iron (II) ions incorporated into the diet.

Write a balanced equation showing the formation of iron (II) ions in an acid solution.

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2 Answers

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Iron is oxidising from the acid from Fe to Fe2+. (Half equation: Fe → Fe2+ + 2e-)

Hence, the acid must reduce. So looking in the electrochemical series for a good acidic oxidant yields this half-equation:

O2 + 4H+ + 4e– → 2H2O

(Because this uses the electrochemical series, it's probably not appropriate for Unit 3 – this is covered in depth in Unit 4, but technically it's a bit of Unit 2 revision too)

So the overall reaction would be:

  • ( Fe → Fe2+ + 2e- ) x 2

  • O2 + 4H+ + 4e– → 2H2O

  • 2Fe + O2 + 4H+ → 2Fe2+ + 2H2O

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What about the ionic equation for this?

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My answer (merspi.com/questions/1299/…) is the ionic equation already. There's no spectator ions there! – Collin Li♦ Feb 23 at 12:23

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