Verifying Nernst Equation Calculation: Pb2+ and Ag+

Click For Summary
SUMMARY

The forum discussion centers on verifying the Nernst equation calculation for the redox reaction involving lead (Pb) and silver (Ag) ions. The standard reduction potentials are given as Estandard(Pb2+/Pb) = -0.13V and Estandard(Ag+/Ag) = 0.80V. The user calculated the cell potential (E) using the Nernst equation but arrived at an incorrect value of 207.56V. The correct approach involves accurately determining the reaction quotient (Q) and applying the Nernst equation correctly to find E.

PREREQUISITES
  • Understanding of the Nernst equation
  • Knowledge of standard reduction potentials
  • Familiarity with electrochemical cell reactions
  • Basic thermodynamics concepts (temperature, gas constant)
NEXT STEPS
  • Review the Nernst equation derivation and applications
  • Learn about calculating reaction quotients (Q) in electrochemistry
  • Study the significance of standard reduction potentials in redox reactions
  • Explore common pitfalls in electrochemical calculations
USEFUL FOR

Chemistry students, electrochemists, and anyone involved in analytical chemistry or electrochemical cell design will benefit from this discussion.

higherme
Messages
126
Reaction score
0
Can anyone check if I am doing this right?

Given:
Pb2+ + 2e- ---> Pb(s) E standard = -0.13V
Ag+ + 1e- ---> Ag(s) E standard = 0.80V

[Pb2+] = 0.05M
[Ag+] = 0.5 M these are non standard concentrations

Temp = 298K

Using the Nernst equation, find E


My answer:

Pb oxidized and Ag is reduced ( is this right?... because Ag has the higher reduction potential compared to Pb)

E = E standard - (RT/nF) ln Q

Q = [products]^p/[Reactants]^r

the reaction is: 2Ag+ + Pb(s) + 2e- ---> 2Ag(s) + Pb2 + 2e- (the electrons cancels out)

therefore, Q = (0.05M) / (0.5)^2

Q= 0.20

the E standard = 0.80 - (-0.13) = 0.80 + 0.13 = 0.93V
E = E standard - (RT/nF) ln Q
E = 0.93 - (8.314*298K/2*9.649E4) ln (0.20)
E= 207.56 V

Can anyone check the calculations for me and see if I am doing this right please?

Thank you!
 
Physics news on Phys.org
higherme said:
Can anyone check if I am doing this right?

Given:
Pb2+ + 2e- ---> Pb(s) E standard = -0.13V
Ag+ + 1e- ---> Ag(s) E standard = 0.80V

[Pb2+] = 0.05M
[Ag+] = 0.5 M these are non standard concentrations

Temp = 298K

Using the Nernst equation, find E


My answer:

Pb oxidized and Ag is reduced ( is this right?... because Ag has the higher reduction potential compared to Pb)

E = E standard - (RT/nF) ln Q

Q = [products]^p/[Reactants]^r

the reaction is: 2Ag+ + Pb(s) + 2e- ---> 2Ag(s) + Pb2 + 2e- (the electrons cancels out)

therefore, Q = (0.05M) / (0.5)^2

Q= 0.20

the E standard = 0.80 - (-0.13) = 0.80 + 0.13 = 0.93V
E = E standard - (RT/nF) ln Q
E = 0.93 - (8.314*298K/2*9.649E4) ln (0.20)
Looks good up to here.

E= 207.56 V
That's way off. Chug those numbers again.
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
3K
Replies
3
Views
10K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 1 ·
Replies
1
Views
10K
  • · Replies 10 ·
Replies
10
Views
4K
Replies
1
Views
3K
Replies
4
Views
6K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
2
Views
5K