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 spontaneous reaction has a positive Gibbs free energy change and a negative emf.
A Gibbs free energy change involves coulombs of substances whereas an emf involves moles of electrons.
A coulomb of particles is more particles than a mole of particles.
The Gibbs free energy change and emf values of a reaction have the same algebraic signs (+ or -).

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) 2 Fe3+(aq) + 2 Hg(l)  2 Fe2+(aq) + 1 Hg22+(aq)

Eo = -0.018 V

Go =  kJ/mol

nonspontaneous

at equilibrium    

spontaneous

(b) 2 K+(aq) + 1 Mn(s)  2 K(s) + 1 Mn2+(aq)

Eo = -1.745 V

Go =  kJ/mol

nonspontaneous

at equilibrium    

spontaneous

(c) 2 Co3+(aq) + 1 Co(s)  2 Co2+(aq) + 1 Co2+(aq)

Eo = 2.119 V

Go =  kJ/mol

nonspontaneous

at equilibrium    

spontaneous

(d) 2 Fe(CN6)3-(aq) + 2 Br-(aq)  2 Fe(CN6)4-(aq) + 1 Br2(l)

Eo = -0.705 V

Go =  kJ/mol

nonspontaneous

at equilibrium    

spontaneous

Answer 1

Answers ). The statement which is correct+. The Gibbse free energy change and emf values of Healt have opposite algebric sigons” (+vs.-). *@). given, Ecell = -0.018V, 163 - MF Edell, where, n = change in electron = 2 in this seaction, now, 16°= -2x96500x(-0.018 V) F= 96500C, 46°= 3474 J/mol = 1Gº= + 3-474 Kipol. Hence, oson spontaneous because OG is tve, (6). n=2, Erell = 0 -1745V, F = 96500.c. 46°= -n Feeell = -2x96500 x(-10745) 14°= 336785 Ilmef = 3360785 KJ/mot. non - spon taneous because 44048 +ve. (C). N=2, F=96500C, Eeell = 20119 V. 16 = - OFE Pell = -2x96500CX 20119 V =-408 967 J/mol. G =- 408.696 kJ/mol. non spontaneous because 16° is fixo. -ve. ud). 7=2, F =96500, Ecell = -0.705 V. .: 46°3 - NF Feella -2x 96 500 € * (-0.905 V).= 136065J/mol. 4Gº = + 136.065 kJ/mol. non- spontaneous because, ta ºis tve.