SI Chem 178
Ch 20
Leader: Emily
April 25, 2013 (Thurs)
Quiz on Friday – work individually, 20 minutes
1. determine spontaneous redox reaction given standard reduction potentials and write the
associated balanced redox equation.
2. calculate standard cell potential Eo and Go given the equilibrium constant K. Relate to
spontaneity of reaction.
3. Identify/rank strengths of oxidizing and/or reducing agents given standard reduction potentials.
Recommended problems for recitation & quiz on Friday:
Chapter 20: 4 - 8, 30, 32, 35, 38d, 39, 41, 43bc, 44bd, 45, 47, 52b, 53, 55c, 58, 61, 63, 68, 69,
74, 75, 77
Review:
20.4 You want to make a voltaic cell using the following half reactions:
A2+(aq) + 2e-  A(s)
Ered =-0.10 V
B2+(aq) + 2e-  B(s)
Ered =-1.10 V
-Draw out a generalized voltaic cell – what all do you need?
-Which is the cathode, anode? Which direction will e- move?
-What is your calculated Ecell?
Complete and balance the following rxn:
BrO3-(aq) + N2H4(g) Br-(aq) + N2(g) Acidic Solution
New Stuff:
If E is +, G is ____________ and the reaction is ______________________
A higher / lower Ered shows preference to be reduced.
Ecell = _________________ - ____________________
In a concentration cell, you have the same / different electrodes.
When concentrations are equal in a concentration cell, the voltmeter will read _________
What is the form of the Nernst equation that we use for concentration cells?
20.43 Which is the stronger reducing agent: Ca(s) or Al(s)
20.44 Which is the stronger oxidizing agent: Zn2+ or Cd2+
20.46 Classify each of the following as being more likely to serve as an oxidant or
reductant:
Ce3+(aq)
Ca(s)
ClO3-(aq)
N2O5(g)
20.53 In a given reaction, the equilibrium constant (K) is 1.5*10^-4 at 298K, calculate
G* and E*red. Also try problem #58
20.69 Concentration Cell: Two Zn electrodes with Zn2+ solutions
Solution 1 at 1.8M and Solution 2 at 0.01M
Which is the cathode, anode (where will Zn2+ increase/decrease)? What is the std EMF?
What is the cell EMF?