Test 2, Question #5

[Hena Sihota 1L]

This problems asks you to rank the following in order of increasing reducing power:
a)Zn, Mn, Cr
b)I₂, Br₂, Al
I understood that the more negative the reduction potential, the greater the reducing power, and applied this logic to both parts.
I wrote out the reduction potentials and ordered them from least negative reduction potential to most negative reduction potential.
a) Zn:-0.76, Mn:-1.18, Cr:-0.74 Cr<Zn<Mn
b)I₂:0.54, Br₂:1.07, Al:-1.66 Br₂<I₂<Al
I got part (b) correct, but I got part (a) wrong. What did I do wrong?

[Ammar Amjad 1L]

Hey, so the potential you've written for Cr should be -0.91 V, the one you've written is the potential for Cr^3+ going to Cr, you need to use the potential from Cr^2+ to Cr. Hope this helps.