Ask questions and get helpful responses.

chem- electrochem-HELP

Given a cell based on the spontaneous reaction
2AgCl(s) + Zn(s) ® 2Ag(s) + 2Cl– + Zn2+
If the zinc ion concentration is kept constant at 1 M, and the chlorine ion concentration is decreased from 1 M to 0.001 M, the cell voltage should
increase by 0.06 V
increase by 0.18 V.
decrease by 0.06 V.
decrease by 0.18 V.
increase by 0.35 V.

i keep getting the wrong answer- none that are listed anyways.
i have put into half-rxn, then used
G=-nFE and the dG=-RT InK, but cannot get the right answer pls help. its for an assignment due tonight- aust time

  1. 👍
  2. 👎
  3. 👁
  4. ℹ️
  5. 🚩
  1. got my questions meixed up!
    I have tried this one by getting the 3 half-rxn and adding them up. then using E=E*-RT/nF InQ. i get close to an answer but not exact. i get 0.088V

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩
  2. Look up E* for Zn (as written). I find 0.763.
    Look up AgCl(s) + e ==> Ag(s) + Cl^- (as written). I find 0.222
    Add to find E*cell. I find 0.985

    Then
    Ecell = E*cell -(0.06/n)log(products/reactants).

    Ecell = E*-(0.06/n)log [(Zn^+2)(Ag)^2(Cl^-)^2/(Zn)(AgCl)]
    Now substitute for
    n = 2
    (Zn^+2) = 1 M
    (Ag) = standard state = 1
    (Cl^-) = 1 M
    (Zn) = standard state = 1
    (AgCl) = standard state = 1
    Plugging all that in gives you the log term of 1, log 1 = 0 and Ecell is just E* = 0.985 v

    Now to the other scenario.
    (Zn^+2) = 1M
    (Ag)(s) = standard state = 1
    (Cl^-) = 0.001 (remember to square it).
    (Zn) = standard state = 1
    (AgCl) = standard state = 1.
    So that part becomes
    Ecell = E*cell - (0.06/2)log(1 x 10^-6)
    Ecell = 0.985 - (0.03)(-6)
    So the change is + 0.18 and that is one of the choices.
    You may have been using 0.0592 which would give you 0.1776 which still rounds to 0.18v.
    (

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩
  3. thank you so much. I stuffed up at the start. i had 3 half-rxn. i didn't see that there was one for AgCl- it all makes thank. thankyou for your patience, It appriciated. I had to cram this subject in to get this assignment done. we are not supposed to start this topic til monday which is when the assignment is due- not fun so again thankyou!

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩

Respond to this Question

First Name

Your Response

Still need help? You can ask a new question.