14.3 Voltaic Cells vs Electrolytic Cells

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VOLTAIC CELLS ELECTROLYTIC CELLS
Spontaneous (ΔG < 0, Ecell > 0) Nonspontaneous (ΔG > 0, Ecell < 0)
Produce Electricity Consume Electricity
Function as Batteries Used to Produce Elements
CHARACTERISTICS OF ELECTROCHEMICAL CELLS
1. The anode is ALWAYS the site of oxidation.                (an ox)
2. The cathode is ALWAYS the site of reduction.             (red cat)
3. Electrons ALWAYS flow from anode to cathode.
4. Anions flow to the anode and cations to the cathode through the salt bridge (in galvanic cells).
5. In galvanic/voltaic cells (spontaneous), the cathode is + and the anode is –.
     In electrolytic cells (nonspontaneous), the cathode is – and the anode is +.
6. The cathode gains mass, while the anode loses mass (for metal/metal salt galvanic cells).
COMMON BATTERIES
Lead Storage Battery PbO2(s) + Pb(s) + 2H2SO4(aq) → 2PbSO4(s) + 2H2O(l)
Anode = Pb      Cathode = PbO2
Hydrogen Fuel Cell 2H2(g) + O2(g) → 2H2O(l)
Anode = H2      Cathode = O2

Electrolytic Cells: Predicting the Products
What are the products of electrolysis of molten NaCl?

What are the products of electrolysis of Al2O3(l)?