Question

Calculate the standard cell potential (E∘) for the reaction X(s)+Y+(aq)→X+(aq)+Y(s) if K = 2.71×10−3.

Answer 1

Solution :

Overall cell reaction is

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

n = Number of electrons involved =1

K = 2.71 E-3

We know

Delta G⁰ = - RTlnK

R = 8.314 J / (mol K )

T = 298.15 K (room T)

Ka is equilibrium constant for this reaction

Lets plug the values and get the Delta G⁰

Delta G⁰ = - [ 8.314 x 298.15 x ln (2.71 E-3)] J

= -(-14651.82 J )

= 14651.82 J

Now using it we get value of E⁰

Delta G⁰ = - nE⁰ F

Here Delta G⁰ is standard free energy change , n = number of electrons involved in overall reaction.

E⁰ standard electrode potential of cell. F is faraday’s constant value is 96500 C / mol

Lets find Delta G⁰

E ⁰ = - Delta G⁰/ n F

= - [14651.82 J / 1 x 96500 ] V

=- 0.152 V

So standard electrode potential of cell = 0.152 V