1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Jones reduction

  1. Aug 19, 2013 #1
    1. The problem statement, all variables and given/known data
    Give the reactions that take place when the following solutions are passed through a Jones-redactor (amalgamated zinc), and calculate the equilibrium constant at 298.15 K for each.
    0.01 mol/dm3 CuCl2
    0.01 mol/dm3 CrCl3
    0.01 mol/dm3 NH4VO3 (pH =1)

    Couple, E° value
    Cu2+/Cu 0.34
    Cr3+/Cr –0.74
    Cu2+/Cu+ 0.16
    Cr2+/Cr –0.90
    VO2+/VO2+ 1.00
    Zn2+/Zn –0.76
    VO2+/V3+ 0.36
    TiO2+/Ti3+ 0.10
    V3+/V2+ –0.255
    Ag+/Ag 0.80
    V2+/V –1.13
    Fe3+/Fe2+ 0.77

    2. Relevant equations

    The usual equations - ΔG=-nFE, ΔG°=-nFE°, ΔG=-RTln(K).

    3. The attempt at a solution


    So one redox equation going on for all cases is the Zn2+/Zn couple, E°=–0.76, Zn2+ + 2e- ::equil:: Zn. The forward reaction will occur if E°[Zn2+/Zn]>E°[Couple j], where j is the couple which represents the redox equation occurring on the other side.

    But how do I know which equation j will be, from all the different choices we get for each case? For example, in the first case, is it Cu2+ + e- -> Cu+, Cu+ + e- -> Cu, or Cu2+ + 2e- -> Cu which we need to consider as couple j against E°[Zn2+/Zn]? And how do we determine which equation we need to take for all three cases. I have seen the solutions but this question, of which one to choose of the possible equations, is not properly explained.
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted