Question

Part 1.)

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.

1. The Gibbs free energy change and emf values of a reaction have opposite algebraic signs (+ vs. -).
2. A mole of particles is more particles than a coulomb of particles.
3. A spontaneous reaction has a positive Gibbs free energy change and a negative emf.
4. A Gibbs free energy change involves moles of substances whereas an emf involves coulombs of electrons.
5. Electron stoichiometry need not be used to interconvert a Gibbs free energy change and a reaction emf.

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 I2(s) + 1 Cd(s) 2 I-(aq) + 1 Cd2+(aq)

Eo = 0.939 V

Go = __ kJ/mol

nonspontaneous, at equilibrium, or spontaneous

(b) 2 Na+(aq) + 1 H2(g) 2 Na(s) + 2 H+(aq)

Eo = -2.710 V

Go = __ kJ/mol

nonspontaneous, at equilibrium, or spontaneous

(c) 3 Ce4+(aq) + 1 Cr(s) 3 Ce3+(aq) + 1 Cr3+(aq)

Eo = 2.350 V

Go = __ kJ/mol

nonspontaneous, at equilibrium, or spontaneous

(d) 2 Cu+(aq) + 1 Hg(l) 2 Cu(s) + 1 Hg2+(aq)

Eo = -0.333 V

Go = __ kJ/mol

nonspontaneous, at equilibrium, or spontaneous

Part 2.)

(a) In the electrolysis of aqueous NaNO₂, how many liters of NO(g) (at STP) are generated by a current of 87.0 A for a period of 61.4 min? The unbalanced chemical reaction representing this electrolysis is shown below.

NaNO₂(aq) + H₂O(l) NO(g) + O₂(g) + NaOH(aq)

___ liters of NO(g) is generated by this electrolysis.

(b) How many moles of NaOH(aq) are formed in the solution in this process?
___ moles of NaOH(aq) are formed.

Answer 1

5) as Basic] Aoi = - DFE Avi -> Free energy n Number of electron transferred const 96.500 Coulomb F Faraday's 965 we get ago in kJ/mol used E = emf of the cell AG = -96-5 AE cel aus. - Spontaneous sco = + room spontaneoy as o equlibrium Noter a) D G ACT' -96.5 x 2 x0.939 -181.2 KJ/mol ALE ENHE) = tnre - - 181.227 = spontaneous (bz -) E =- suat Non spontanes b " Ano = -96.5 x 2 x 1-2.710) = + 523.03 kJ/mol = Non spontaneous Coz Av=+) 3) smo = -96.5 x 3 x 2.35 =-680.325 kJ/mol = spontaneous d 4 ano = -96.5 x 2 x -0.333 + 646289 = 643 kJ/mol Non spontaneous (bz anet) 11