Chemistry 104 Laboratory
	This Week
Answer Keys Gen Chem Lab Periodic Table	· Expt 9: Electric Metal Art, Part I
	Next Week
	· Expt 8: Nanocrystalline Solar Cells · Quiz 5: Experiments 5,6
	Notes for Today
	Redox Rxn: Zn(s) + 2 H^+ (aq) --> Zn^2+(aq) + H2 (g) reduction = gain of electrons: 2H^+ + 2e- --> H2 oxidation = loss of electrons: Zn --> Zn^2+ + 2e- reducing agent is oxidized and is the source of e-: Zn oxidizing agent is reduced and is the acceptor of e-: H^+ Electrochemical Cell Based on the Rxn: Zn(s) + 2H^+ (aq) --> Zn^2+(aq) + H2 (g) anode = electrode where e- are generated cathode = electrode where e- are consumed Cell Notation: Zn(s)| Zn^2+(aq) || H^+ (aq)| H2 (g)| Pt left to right: oxidation half cell || reduction half cell | = surface or phase change || = salt bridge Current Flow Within the Cell must be a complete circuit e- movement in electrical conductors (wire/electrodes) ion movement in solution (salt bridge/half cell solution) Two Types of Cells voltaic or galvanic cell spontaneous cell rxn, e.g. Zn + 2H^+ --> Zn^2+ + H2 Ecell is positive energy released as cell operates electrolytic cell non-spontaneous cell reaction, e.g. Zn^2+ + H2 --> Zn + 2H^+ E cell is negative Power source is required to force rxn Calculating the Standard Cell Potential (E^ocell): Rxn: Zn(s) + 2 H^+ (aq) --> Zn^2+(aq) + H2 (g) Look up standard reduction potentials (E^o values, in your textbook): 2H^+ + 2e- --> H2 E^ored = 0.000v Zn^2+ + 2e- --> Zn E^ored = -0.763v Convert one reduction to the oxidation that actually occurs in rxn 2H^+ + 2e- --> H2 E^ored = 0.000v Zn --> Zn^2+ + 2e- E^oox = +0.763v Sum the standard (half) potentials to get E^ocell E^ocell = E^ored + E^oox = +0.763v Time Management Sketch and write equations as you work. Safety Recycle reagents in designated containers. Goggles Required