- #1
pzona
- 234
- 0
This problem is homework from a lab I did yesterday. Normally I would just ask my TA, but since it's homework I can't. I could email him, but I feel like I'll probably get a faster response if I post this here
Use the Nernst equation to determine the cell potential for the cell involving Ag+. This is from a voltaic cell I made using a copper anode and CuSO4 solution and a silver cathode and AgNO3, with a KNO3 solution as a salt bridge. I used a multimeter to calculate the cell potentials for other cells I built (using other metal cathodes and relevant solutions) because their concentrations were 1M, standard conditions. The AgNO3 was 0.1M so I need to use the Nernst equation to calculate cell potential (assuming all other factors, ex. temperature were standard).
Measured potential for the cell: -0.390V
Given oxidation potential for the copper half reaction: +0.34V
The Nernst Equation:
E_{cell} = E^{o}_{cell} + 0.0592V(mol)/n * log_{10}Q
Half reaction at the cathode:
Ag+(aq) + e- -> Ag(s), since [Ag+] = 0.1M, Q and n will both be 0.1
Honestly, this comes down to me not understanding what the terms mean. I just started electrochemistry and I haven't been able to find a decent explanation of the terms online.
I'm not sure whether I need to solve for E^{o}_{cell} (I did and got -0.982V) or E_{cell} (I got +0.202V). Solving for E^{o}_{cell} makes more sense, given my answer, since I know that silver is a poor reducing agent. It should give a negative answer of fairly high magnitude in relation to the other cells, which it did.
Basically what I'm asking is, E^{o}_{cell} is the quantity I'm looking for...right? Is E_{cell} the measured potential for a cell under non-standard conditions? Also, is my answer for E^{o}_{cell} of a reasonable magnitude? Thanks.
EDIT: Looks like my subscripts were messed up somehow. I'm pretty sure you'll be able to figure out what I meant though.
Homework Statement
Use the Nernst equation to determine the cell potential for the cell involving Ag+. This is from a voltaic cell I made using a copper anode and CuSO4 solution and a silver cathode and AgNO3, with a KNO3 solution as a salt bridge. I used a multimeter to calculate the cell potentials for other cells I built (using other metal cathodes and relevant solutions) because their concentrations were 1M, standard conditions. The AgNO3 was 0.1M so I need to use the Nernst equation to calculate cell potential (assuming all other factors, ex. temperature were standard).
Measured potential for the cell: -0.390V
Given oxidation potential for the copper half reaction: +0.34V
Homework Equations
The Nernst Equation:
E_{cell} = E^{o}_{cell} + 0.0592V(mol)/n * log_{10}Q
Half reaction at the cathode:
Ag+(aq) + e- -> Ag(s), since [Ag+] = 0.1M, Q and n will both be 0.1
The Attempt at a Solution
Honestly, this comes down to me not understanding what the terms mean. I just started electrochemistry and I haven't been able to find a decent explanation of the terms online.
I'm not sure whether I need to solve for E^{o}_{cell} (I did and got -0.982V) or E_{cell} (I got +0.202V). Solving for E^{o}_{cell} makes more sense, given my answer, since I know that silver is a poor reducing agent. It should give a negative answer of fairly high magnitude in relation to the other cells, which it did.
Basically what I'm asking is, E^{o}_{cell} is the quantity I'm looking for...right? Is E_{cell} the measured potential for a cell under non-standard conditions? Also, is my answer for E^{o}_{cell} of a reasonable magnitude? Thanks.
EDIT: Looks like my subscripts were messed up somehow. I'm pretty sure you'll be able to figure out what I meant though.