- Galvanic cell = battery → provide power
- REDOX reactions can be used to convert chemical energy into electrical energy
Can use two half reactions and cause electrons to flow through a wire (electricity)
- With this set up (→), the system will start but then stop immediately BCUZ will have a build up of positive change in the left half cell and buildup of negative charge in right half cell
For a circuit to flow, need a constant flow of charge
- Salt bridge fixes the above problem → allows spectator (not part of redox reaction) ion migration
○ Spectator ions wont be oxidized or reduced; Cations → cathode; anions → anode
- In the Anode solid atoms of zinc are being converted into aqueous zinc (oxidation) & deposited into the solution→ zinc bar is losing mass over time
○ Justify: Oxidation is taking place (electrons are being released)
- In the Cathode aqueous copper ions are being converted into solid copper (reduction) and are deposited into the cathode → the mass of the electrode will increase over time
○ Justify: Reduction is taking place (electrons are being consumed)
- What if species involved in galvanic cell reaction are not solid (liquid, aqueous, or gas)?
A solid electrode is still needed → usually platinum or graphite are used bcuz they are conductive but mostly unreactive
- Electrode & half-cell questions:
○ Remove an electrode → voltage becomes zero and remains there
○ Changing the mass of a solid electrode will have no change on the E° b/c chemical reaction won’t change
○ If both half-reactions have the same reduction potentials (ex: both -) → voltage wont stop but cell potential will decrease
- Electrons always flow from anode to cathode (“from A to C”)
- Drawing half-cells:
○ Must indicate changes in (aq) and electrode (s); include spectator ion
○ The total charge must equal 0