Question

Calculate the standard cell potential at 25 ∘C for the reaction X(s)+2Y+(aq)→X2+(aq)+2Y(s) where ΔH∘ = -597 kJ and ΔS∘ = -337 J/K

Answer 1

Solution-

Given

ΔS∘ = -337 J/K

ΔH∘ = -597 kJ = -597000 J

T = 25 ° c = 298 K

Faraday constant (F) = 96500 J

Let’s write the given cell reaction

X(s) + 2Y+(aq) --> X2+(aq) + 2Y(s)

We know the equation of Gibbs free energy and the emf (potential) of a cell .

ΔG = -nFE

Here n = number of moles = 2

X goes from X(0) to X(2+)

We also knows the other equation of ΔG

ΔG = ΔH - T ΔS = (-597000 J) – 298 *(-337 J/K)

ΔG = -496574 J

Now insert the ΔG value in first equation

ΔG = -nFE

-496574 J = (- 2 ) * 96500 J * E

E = (-496574 J)/(-193000 J)

E = 2.57 Volts

Answer: standard cell potential at 25 ∘C for the reaction = 2.57 Volts