# Redox titration or iron(II)

1. The concentration of $$\ce{Fe^2+(aq)}$$ can be determined by a redox titration using

A. $$\ce{KBr}$$
B. $$\ce{SnCl2}$$
C. $$\ce{KMnO4}$$ (basic)
D. $$\ce{KBrO3}$$ (acidic)

Can anyone please help me on this question? I know the answer is between C and D, since those two are the only redox reactions. However, I don't know how to determine between C and D, as they will both act as an oxidizing agent and Fe will be reduced in both cases (the correct answer is D).

• This question requires some background chemistry knowledge. First of all, think whether the presence of base will interfere or not. Will iron(II) precipitate out as a hydroxide? We wouldn't like to do titration in a heterogeneous mixture. The next to keep in mind is electrode potentials of permanganate and bromate half cells. Jun 9 '19 at 3:42
• May I ask for clarifications to electrode potentials? do you mean I should calculate for the overall E value of the reaction? Jun 9 '19 at 3:57
• Can you please elaborate on that part? I know that the E value of Mno4- is +1.51, and the one for BrO3- is +1.48. What does that suggest?? that Mno4- will more likely to be reduced by Fe+ than Bro3-?? please explain Jun 9 '19 at 4:04
• Did you understand what is the reductive electrode potentials are? By the way, $\ce{Fe}$ won't reduce in any case (as you suggested). Jun 9 '19 at 4:10
• Yes i do. I guess I dont understand the role that acid and base play in redox reactions. When doing a titration, how do I know when to use an acidic medium and when to use a basic one? I dont understand how looking at half cells potentials can allow me to determine this Jun 9 '19 at 4:22