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# Solutions

1. Write the cell diagram for the Cu+2/Cu and Al+3/Al half-cells and calculate the Eocell for the Cu+2/Cu and Al+3/Al half-cells.

 Write half-reactions with more negative on top: Al+3 (aq) + 3 e- -------> Al (s) Eo= -1.66 V Cu+2 (aq) + 2 e- -------> Cu (s) Eo= +0.34 V Species on bottom left reacts with species above and to the right, therefore switch top reaction and change sign of Eo Al (s) -------> Al+3 (aq) + 3 e- Eo= +1.66 V (anode) Cu+2 (aq) + 2 e- -------> Cu (s) Eo= +0.34 V (cathode) Add cell potentials of half-reactions to determine Eocell Eocell= +2.00 V

cell diagram (anode first):

Al (s) | Al+3 (aq, 1M) || Cu+2 (aq, 1 M) | Cu (s)

2. Write the cell diagram and calculate the Eo for the Zn/ Zn+2 and Ca/Ca+2 half-cells.

Eo= 2.11 V
cell diagram:
Ca (s) | Ca+2 (aq, 1M) || Zn+2 (aq, 1 M) | Zn (s)

 3. a) Will I- react with Br2? Yes b) Will Ni+2 react with Br2? No c) Will Ni react with Br2? Yes Will Co+2 react with Br2 to give Co+3? No, reacts with Co+2 to give Co (s)

4. Rank the following ions from strongest to weakest oxidizing agents:

 Eo , V Ag+ strongest + 0.80 Pb+2 - 0.13 Al+3 - 1.66 Sr+2 - 2.89 Li+ weakest - 3.05

5. Determine the E for the Ag+/Ag and Sn+2/Sn half-cells if the [Ag+] = 1.0 M and the [Sn+2] = 0.25 M.

 Write half-reactions with more negative on top: Sn+2 (aq) + 2 e- -------> Sn (s) Eo= -0.14 V Ag+ (aq) + 1 e- -------> Ag (s) Eo= +0.80 V Species on bottom left reacts with species above and to the right, therefore switch top reaction and change sign of Eo Sn (s) -------> Sn+2 (aq) + 2 e- Eo= +0.14 V (anode) Ag+ (aq) + 1 e- -------> Ag (s) Eo= +0.80 V (cathode) Add cell potentials of half-reactions to determine Eocell Eocell= +0.94 V To determine E, use Nernst equation: E = Eo-(0.0591/n)log Q E = Eo-(0.0591/n)log Q; n = 2 (make e- lost = e- gained in the half-reactions); Q = [Sn+2]/ [Ag+]2([Sn+2] is on the product side, [Ag+] is on the reactant side after switching half-reactions) E = 0.94V -(0.0591 V/2)log {0.25M Sn+2/ (1.00 Ag+)2} E = 0.958 V

6. Is the reaction below spontaneous? no Calculate the Eo. Eo = - 0.47 V

Pb+2 + Cu ------> Pb + Cu+2

7. Determine the $$\Delta{G}^o$$ for the Ag+/Ag and Sn+2/Sn half-cells.

missing...anyone want to do this?

8. Calculate $$\Delta{G}^o$$ for Cu+2/Cu and Mn+2/Mn half-cells. Is this reaction spontaneous?

Eo = 1.52 V;

$$\Delta{G}^o = -293,360 J$$

or

$- 293.4 \, kJ$

Yes, this reaction is spontaneous as written.

5. Calculate $$\Delta{G}$$ for Ni+2/Ni and Fe+2/Fe half-cells if the [Ni+2] = 0.25 M and the [Fe+2] = 0.50 M.

Eo = 0.19 V; E = 0.181 V; DG = - 34956 J or - 35.0 kJ

6. Determine the $$\Delta{G}$$ for the Al+3/Al and Ni+2/Ni half-cells.if the [Al+3] = 0.50 M and the [Ni+2] = 0.25 M.

Eo = 1.41 V; E = 1.398 V; $$\Delta{G}$$ = - 809442 J or - 809.4 kJ