Question

(a) Choose all of the statements from below which correctly describe issues pertaining to the relationship between the emf of a reaction and its Gibbs free energy change.

The Gibbs free energy change and emf values of a reaction have opposite algebraic signs (+ vs. -).
A Gibbs free energy change involves moles of substances whereas an emf involves coulombs of electrons.
The Gibbs free energy change and emf values of a reaction have the same algebraic signs (+ or -).
Faraday's constant is used to interconvert coulombs of electrons and moles of electrons.
A coulomb of particles is more particles than a mole of particles.

Calculate the standard Gibbs free energy changes at 25 ^oC for each of the reactions shown below using the E^o values given. Select whether each of these reactions is nonspontaneous, at equilibrium, or spontaneous under standard conditions.

(a) 1 Hg2+(aq) + 2 Ce3+(aq) 1 Hg(l) + 2 Ce4+(aq)

Eo = -0.756 V

Go =  kJ/mol

nonspontaneousat equilibrium     spontaneous

(b) 2 Hg2+(aq) + 1 Sn(s) 1 Hg22+(aq) + 1 Sn2+(aq)

Eo = 1.056 V

Go =  kJ/mol

nonspontaneousat equilibrium     spontaneous

(c) 2 Al3+(aq) + 3 H2(g) 2 Al(s) + 6 H+(aq)

Eo = -1.660 V

Go =  kJ/mol

nonspontaneousat equilibrium     spontaneous

(d) 1 Ni2+(aq) + 2 Cl-(aq) 1 Ni(s) + 1 Cl2(g)

Eo = -1.639 V

Go =  kJ/mol

nonspontaneousat equilibrium     spontaneous

Answer 1

Eu = – 0.156 v AGO = – nf to na 2 (no of electors transferred - - 2 X 96500x (-0.756) ono = 145.91 KJ ! (non-spontaneous) 6) AGO – OFEoE – 2 x 96500X (1.056) Toho = - 203.81 ko) (spontaneous) c) suo = -nf to = – 6896500X (-1166) Tsuo = 961114 K5 all (non-spontaneous) d) Duo- - nf to = - 2x 965000 (-1.639) I Duo - 316.327 ICJ (non-spontaneous)