Answer :
Answer:
1. 0.559 V
2. 0.514 V
Explanation:
Nernst Equation - Can be used to find the cell potential at any moment in during a reaction or at conditions other than standard-state.
E = E₁ - RT/nF ㏑Q
E = cell potential (V) under specific conditions
E₁= cell potential at standard-state conditions
R = ideal gas constant = 8.314 J/mol-K
T = temperature (kelvin), which is generally 25C (298 K)
n = number of moles of electrons transferred in the balanced equation
F = Faraday's constant, the charge on a mole of electrons = 95,484.56 C/mol
lnQ = the natural log of the reaction quotient at the moment in time
First calculate E₀ for the cell.
Zn(s) ==> Zn²⁺(aq) + 2e⁻ . . .E₀ = +0.76 V
Ni⁺²(aq) + 2e⁻ ==> Ni(s) . . . E₀ = -0.23 V
Zn(s) + Ni⁺²(aq) ==> Zn⁺²(aq) + Ni(s) . .E₀ cell = +0.53 V
Then use the Nernst equation:
E cell = E₀ cell - 0.059/n log Q = 0.53 - 0.059/2 log ([Zn⁺²]/[Ni⁺²]) = 0.53 - 0.0295 log (0.200/2.0) = 0.559 V
For the second set of conditions,
E cell = 0.53 - 0.0295 log (0.999/0.290) = 0.514 V
The emf of the cell when [Ni2+]= 0.290 M and [Zn2+]= 0.999 M is mathematically given as
E cell= 0.514 V
What is the emf of the cell when [Ni2+]= 0.290 M and [Zn2+]= 0.999 M ?
Generally, the equation for the Chemical reaction is mathematically given as
Zn(s)+Ni2+(aq)→Zn2+(aq)+Ni(s).
Therefore
Zn(s) --> Zn2⁺(aq) + 2e- . . .E₀ = +0.76 V
Ni⁺2(aq) + 2e⁻ ---> Ni(s) . . . E₀ = -0.23 V
hence
E cell = E₀ cell - 0.059/n log Q
E cell = 0.53 - 0.059/2 log ([Zn⁺²]/[Ni⁺²])
E cell = 0.53 - 0.0295 log (0.200/2.0)
E cell = 0.559 V
In conclusion
E cell = 0.53 - 0.0295 log (0.999/0.290)
E cell= 0.514 V
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