(19) Chemistry - Science (Dr. Bob222)

posted by .

Use the following information to answer this question:
Cu+(aq) + e- → Cu(s) E° = 0.521V
Cu2+ (aq) + e- → Cu+ (aq) E° = 0.153 V.
Given these half cell reactions, an aqueous solution of Cu+ ion in the absence of O2(g) :
A. will be thermodynamically stable
B. will almost entirely oxidize to form Cu2+
C. will almost entirely reduce to form Cu(s)
D. will disproportionate to form 50% Cu(s) and 50% Cu2+
E. will reduce water to H2 gas

Chemistry - Science (Dr. Bob222) - DrBob2222, Saturday, May 3, 2014 at 12:12pm

I am torn between answers C and D. I rule out D on the basis of the 50% so I would choose C. I calculated K for C and it is about 10^8 while K for D is about 10^6 if I didn't goof on the math. Check out my thinking since I have this doubt in my mind.

Chemistry - Science (Dr. Bob222) - Ana, Saturday, May 3, 2014 at 12:17pm
the correct answer is D, but i am confused on the rational here. Not sure what the professor wants me to understand here, the concept behind...

Chemistry - Science (Dr. Bob222) - DrBob222, Saturday, May 3, 2014 at 11:08pm
Thanks. I just didn't think the 50% could be right.
The concept behind disproportionation is that an element in an "intermediate" oxidation state (in this case Cu^+ is halfway between Cu below it and Cu^2+ above it) can "react with itself" if the potentials are right. In the case of Cu we would have

Cu^+ ==> Cu^2+ + e E = -0.153
Cu^+ + e ==> Cu E = +0.521
So the cell reaction will be
Cu^+ + Cu^+ ==> Cu + Cu^2+ with a positive voltage of 0368v.
In other words one Cu^+ is oxidized and one Cu^+ is reduced.
I started to leave the question but thought better about it IF I noted I was unsure about the answer. The reason I was unsure was because of the 50% statement so I calculated K and found K for this reaction was about 100 times less than for K for answer C. What I forgot was that C couldn't be right with the possibility of disproportionation since SOME of it would disproportionate so C couldn't be right. And the 50% statement is true since for every Cu^+ that gets reduced another one gets oxidized. 50% on the nose. Cu^+ isn't the only ion that does this. I think Hg2Cl2 does it. Hydrogen peroxide disproportionates. You can read more about it here.


Chemistry - Science (Dr. Bob222) - Ana, Sunday, May 4, 2014 at 9:26am

Thank you for such a great response! You are a legend!

  • (19) Chemistry - Science (Dr. Bob222) -

    Good morning,

    Could you please let me know how did you calculated K for answer D and C. Thank you.

  • (19) Chemistry - Science (Dr. Bob222) -

    RTlnK = nFEo

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry

    I think these I know how to do ....just want someone to check..still sorta mixed up on the first question. Thanx For the following reaction, what is the correctly balanced reduction half-reaction?
  2. Chemistry

    For the following electrochemical cell, what is the correct, balanced reaction?
  3. chemistry

    what is the oxidation half reaction, reduction half reaction, and the complete balanced reaction of the following?
  4. chemistry

    How do you calculate the theoretical cell voltage?
  5. Chemistry

    Given the following half-reactions and associated standard reduction potentials: AuBr−4(aq)+3e−→Au(s)+4Br−(aq) E∘red=−0.858V Eu3+(aq)+e−→Eu2+(aq) E∘red=−0.43V IO−(aq)+H2O(l)+2e−→I−(aq)+2OH−(aq) …
  6. chemistry - Science

    A zinc-copper battery is constructed as follows (standard reduction potentials given below): Zn | Zn2+ (0.10 M) || Cu2+ (2.50 M) | Cu Zn2+ + 2 e- → Zn(s) Eº = -0.76 V Cu2+ + 2 e- → Cu(s) Eº = 0.34 V The mass of each electrode …
  7. chemistry - Science

    A zinc-copper battery is constructed as follows (standard reduction potentials given below): Zn | Zn2+ (0.10 M) || Cu2+ (2.50 M) | Cu Zn2+ + 2 e- → Zn(s) Eº = -0.76 V Cu2+ + 2 e- → Cu(s) Eº = 0.34 V The mass of each electrode …
  8. Chemistry - Science (Dr. Bob222)

    Use the following information to answer this question: Cu+(aq) + e- → Cu(s) E° = 0.521V Cu2+ (aq) + e- → Cu+ (aq) E° = 0.153 V. Given these half cell reactions, an aqueous solution of Cu+ ion in the absence of O2(g) : …
  9. Chemistry - Science (Dr. Bob222)

    Posted by Ana on Saturday, May 3, 2014 at 11:23am. A zinc-copper battery is constructed as follows (standard reduction potentials given below): Zn | Zn2+ (0.10 M) || Cu2+ (2.50 M) | Cu Zn2+ + 2 e- → Zn(s) Eº = -0.76 V Cu2+ + …
  10. chemistry

    Which of the following half-reactions would occur at the anode of an electrochemical cell?

More Similar Questions