A. Look up and report K f for copper(II), iron(II), and iron(III) with EDTA. Cit

Question

A. Look up and report Kf for copper(II), iron(II), and iron(III) with EDTA. Cite your reference(s). (0.2) (I DID THIS ALREADY)

B. What happens to your titration and results if any of those metals are present? Write a balanced chemical equation showing the impact of iron(III) present in the tap water when you are analyzing for calcium. (0.4)

C. What is done to keep iron ions from interfering? Write a balanced chemical equation for this reaction. (0.4)

D. What is done to keep copper ions from interfering? Write a balanced chemical equation for this reaction. (0.4)

Please help!!!! I really want to understand this

Explanation / Answer

1)

Both the hexa–aqua ions of iron(II) and iron(III) readily complex with EDTA

                          Kstab = {[Fe(EDTA)3]2–(aq)} / {[Fe(H2O)6]2+(aq)} [EDTA4–(aq)]

                         Kstab = 2.0 x 1013 mol–1 dm3and lg(Kstab) = 14.3

                        Kstab = {[Fe(EDTA)3]–(aq)} / {[Fe(H2O)6]3+(aq)} [EDTA4–(aq)]

                        Kstab = 1.3 x 1025 mol–1 dm3and lg(Kstab) = 25.1

Note that the more highly charged Fe3+(aq) ion complexes more strongly than the Fe2+(aq) ion.

2) iron 3 will interfere

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