1. Write the net cell equation:
Half-reactions:
Co²⁺(aq) + 2e⁻ → Co(s) (Cobalt reduction)
Ag⁺(aq) + e⁻ → Ag(s) (Siver reduction)
Multiplying the second reaction by 2 to make the number of electrons equal:
Co²⁺(aq) + 2e⁻ → Co(s)
2(Ag⁺(aq) + e⁻ → Ag(s))
Adding the two half-reactions:
Co²⁺(aq) + 2Ag⁺(aq) → Co(s) + 2Ag(s)
2. Calculate the following values at 25 degrees Celsius. Eocell, Ecell, deltaGo rxn, and delta Grxn:
E0cell is the difference in standard reduction potential of the two half-reactions. Using the standard reduction potentials (look up from a table):
E0(Co²⁺/Co) = -0.28 V
E0(Ag⁺/Ag) = +0.80 V
E0cell = E0(Ag⁺/Ag) - E0(Co²⁺/Co) = 0.80 V - (-0.28 V) = 1.08 V
To calculate Ecell, use the Nernst equation:
Ecell = E0cell - (RT/nF) * ln(Q)
Where R is the gas constant = 8.314 J/(mol K), T is the temperature in Kelvin (25 degrees Celsius = 298 K), n is the number of moles of electrons transferred (2 in this case), F is Faraday's constant = 96,485 C/mol and Q is the reaction quotient, given by:
Q = [Co²⁺]/[Ag⁺]^2 = 0.0155 M / (2.50 M)^2
Ecell = 1.08 V - (8.314 J/(mol K) * 298 K / (2 * 96485 C/mol)) * ln(0.0155 / (2.5^2))
Ecell ≈ 1.08V - 0.0120 V = 1.068 V
To calculate deltaGo rxn (the standard Gibbs free energy change), use the equation:
deltaGo rxn = - nFE0cell
deltaGo rxn = -(2 mol e⁻)(96485 C/mol)(1.08 V)
deltaGo rxn ≈ -208 kJ/mol
To calculate delta Grxn (the Gibbs free energy change under nonstandard conditions), use the equation:
delta Grxn = - nFEcell
delta Grxn = -(2 mol e⁻)(96485 C/mol)(1.068 V)
delta Grxn ≈ -206.8 kJ/mol
So, the values for the given electrochemical cell at 25 degrees Celsius are:
E0cell = 1.08 V
Ecell = 1.068 V
deltaGo rxn = -208 kJ/mol
delta Grxn = -206.8 kJ/mol
For the following electrochemical cell, Co(s)/Co2(aq,.0155M)// Ag+(aq,2.50M)/Ag(s)
1.Write the net cell equation.
2.Calculate the following values at 25 degrees celcius. Eocell, Ecell, deltaGo rxn, and delta Grxn
1 answer
1 answer