Answer to Question #183304 in Physical Chemistry for Rebecca

Question

How do I calculate delta E° of the equation Cl2 + 2Br2 = 2Cl. As well is it a spontaneous or non-spontaneous reaction at standard conditions?

Answer 1

The shorthand notation, Cl / Cl²⁺(aq), 1 M // Br²⁺(aq), 2.0 M / Br, means the following:In the anode compartment, Cl(s) --> Cl²⁺(aq) + 2 e^-

In the cathode compartment, Cl²⁺(aq) + 2 e^- --> Cl (s)

Thus, the overall reaction is: Cl(s) + Br²⁺(aq) --> Cl²⁺(aq) + Br(s)

Q = [Cl²⁺] / [Br²⁺]

Nernst equation: E = E⁰ - (0.0592/n) log Q

For the above reaction, n = 2, and E⁰ = E⁰(cathode) - E⁰ (anode) [using standard reduction potentials]

E⁰ = 0.34 V - (-0.76 V) = 1.10 V

E = 1.10 V - (0.0592/2) log (0.1/1.0) = 1.13 V

It is non-spontaneous at standard conditions