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For this question, I thought the correct answer is A, because if we look at the electrode potential, that of iron(III) is higher than that of iodine, therefore the equilibrium for $\ce{Fe^3+}$ will favor the RHS, and shifts to the right, and therefore iodine will go in the opposite direction. Therefore A would be correct.

But the correct answer is D. Using the same logic, I can see it is also correct, but why isn't A correct then?

Thank you for any ideas in advance and sorry for the trivial question.


The reason is simply semantics. Iodi(n)e which is the neutral valence state of the element will not donate an electron to reduce $\ce{Fe^3+}$ to $\ce{Fe^2+}$. Iodi(d)e which is the anionic form of iodi(n)e has a negative charge and can donate an electron to reduce $\ce{Fe^3+}$ to $\ce{Fe^2+}$.


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