1) Balance the redox reaction occurring in basic solution. Cl2(g)+Mn2+(aq)MnO2(s

Question

1) Balance the redox reaction occurring in basic solution.   
Cl2(g)+Mn2+(aq)MnO2(s)+Cl(aq)
Express your answer as a chemical equation. Identify all of the phases in your answer.

2) Use tabulated electrode potentials to calculate G  for the reaction.
2Li(s)+2H2O(l)H2(g)+2OH(aq)+2Li+(aq)
Express your answer to three significant figures and include the appropriate units.

3) Refer to the following standard reduction half-cell potentials at 25C:
Ni2+(aq)+2eNi(s)E=0.23V
VO2+(aq)+2H+(aq)+e VO2+(aq) +H2O(l) E=0.99V

An electrochemical cell is based on these two half-reactions:

Oxidation: Ni(s)Ni2+(aq,2.3M)+2e
Reduction:VO2+(aq,0.048M)+2H+(aq,1.0M)+eVO2+(aq,2.3M)+H2O(l)

Calculate the cell potential under these nonstandard concentrations.
Express the cell potential to two decimal places and include the appropriate units.
E cell = _______ Units

4) Silver can be plated out of a solution containing Ag+ according to the half-reaction

Ag+(aq)+eAg(s)

How much time (in minutes) does it take to plate 13 g of silver using a current of 3.5 A ?

Explanation / Answer

2)

anode reaction: oxidation takes place

2Li(s) ------------------------->2 Li+ (aq) + 2e-   ,   E0Li+/Li = - 3.04 V

cathode reaction : reduction takes palce

2H2O (aq) + 2e- -----------------------------> H2(g) + 2OH- , E0 = -0.828V

--------------------------------------------------------------------------------

E0cell= E0cathode- E0anode

        = -0.828 + 3.04

        = 2.212 V

G = -nF Ecell0

              = - 2 x 96, 500 x 2.212

              = -426916 J

              = - 427 kJ

3)

Eo = 0.99 +0.23 = 1.22 V

Oxidation: Ni(s)Ni2+(aq,2.3M)+2e

Reduction:VO2+(aq,0.048M)+2H+(aq,1.0M)+eVO2+(aq,2.3M)+H2O(l)

Ecell = E0cell -(0.0591/n)* log [Ni+2] [VO+2]^2 / [VO+2]^2 [H+]^2

Ecell = 1.22 - (0.059 x1/2) *log {[2.3] [2.3]^2 / [0.048]^2 }

Ecell   = 1.11

cell potential =Ecell   = 1.11 V

4)

w = 13 g

i = 3.5 A

F = 96485 C

E for Ag = 108

faraday law

w = E x i x t /96485

13 = 108 x 3.5 x t /96485

t = 3318.27 sec

t = 55.3 min

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