You will have to completely label a diagram to look like this Cells and Voltage You will have to completely label a diagram to look like this

Half-cell Anode Cathode Electrolyte Salt bridge Line notation OUTCOME QUESTION(S): C12-6-09 CELLS AND POTENTIALS Explain the operation of a voltaic (galvanic) cell at the visual, particulate and symbolic level. Include: writing half-cell reactions and overall reaction Calculate standard cell potentials and predict spontaneity of reactions. Compare and contrast voltaic (galvanic) and electrolytic cells. Vocabulary & Concepts Half-cell Anode Cathode Electrolyte Salt bridge Line notation

Beginnings of a battery – called a “cell” Volta (1745-1827) Created an electrical current with a spontaneous redox reaction from stacks of metals – voltaic pile Voltaic cells (also called Galvanic cells) convert chemical energy into electrical energy Beginnings of a battery – called a “cell” Metals are separated – called “half-cells” Transfer of electrons forced through wire Load can be run when connect to wire

An electrochemical cell (battery) made with 2 metals, separated into half-cell beakers Electric current (I) – electrons transferred between metals through conducting wire. Voltage (V) – measure of the energy per group of transferred electrons - electrical potential (Eo)

node – electrode where xidation occurs o The following applies to ALL electrochemical cells A node – electrode where xidation occurs o e- produced – negative electrode athode – electrode where eduction occurs C r e- consumed – positive electrode An electrode is just a conducting metal in a cell

2 Ag+(aq) + Cu(s) → 2 Ag(s) + Cu2+(aq) electrons move from copper anode to silver cathode ("A to C")

The following applies to ALL electrochemical cells Anode loses mass: metal loses electrons becoming ion: (s) (aq) ions dissolve in solution: slowly “used up” Cathode gains in mass: ions gain electrons becoming solid: (aq) (s) metal precipitates: “Plate out” onto cathode The following applies to ALL electrochemical cells

Anode loses mass - “used up” Cathode gains in mass - “Plate out” Battery “dies” – the anode metal is all used up: No more electrons to transfer

Salt bridge - maintains charge balance (neutrality) filled with an electrolyte (solution of ions) allows movement of ions, without mixing cells neutralizes the products of each half-cell Ions build-up in both half-cells as the cell operates – if a half-cell gets too (+) or too (–), electrons will stop moving through the wire

Anode – creation of positive ions Cathode – loss of positive ions (leaves behind negative ions) Excess ions in the solution are neutralized by the ions of the salt bridge allowing the redox reaction to continue

3 Pb2+(aq) + 2 Al(s) → 3 Pb(s) + 2 Al3+(aq) Build this battery: 3 Pb2+(aq) + 2 Al(s) → 3 Pb(s) + 2 Al3+(aq) Anode/Cathode Half reactions Ion movement Electron movement Salt bridge ions Al Pb NO3- K+ Al  Al3+ + 3e- Pb2+ + 2e- Pb Al3+ Pb2+

2 Ag+(aq) + Cu(s) → 2 Ag(s) + Cu2+(aq) Line notation short hand notation of the half-cells of a reaction 2 Ag+(aq) + Cu(s) → 2 Ag(s) + Cu2+(aq)

Identify the anode and cathode. Draw an electrochemical cell with Cu oxidizing Zn and complete the following: Identify the anode and cathode. Write the net equation for the reaction. What direction do the electrons move? What is the line notation? If you are not given the form of something - copper (I) or copper (II) – look at the Periodic Table and use the most common type

Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) 1. Copper is the cathode – reduction. Zinc is the anode – oxidation. 2. Oxidation: Zn(s) → Zn2+(aq) + 2 e– Reduction: Cu2+(aq) + 2 e– → Cu(s) Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) If the electrons are not equal multiply by coefficients to make them equal before adding half-cells (like when balancing) 3. e- move from AC: zinc to copper. 4. Zn(s) / Zn2+(aq) // Cu2+(aq) / Cu(s)

Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) Anode/Cathode Half reactions Ion movement Electron movement Salt bridge ions Zn Cu NO3- K+ Zn  Zn2++ 2e- Cu2+ + 2e- Cu Zn2+ Cu2+

Half-cell Anode Cathode Electrolyte Salt bridge Line notation CAN YOU / HAVE YOU? C12-6-09 CELLS AND POTENTIALS Explain the operation of a voltaic (galvanic) cell at the visual, particulate and symbolic level. Include: writing half-cell reactions and overall reaction Calculate standard cell potentials and predict spontaneity of reactions. Compare and contrast voltaic (galvanic) and electrolytic cells. Vocabulary & Concepts Half-cell Anode Cathode Electrolyte Salt bridge Line notation