SAI Galvanic Cells

SRP §

• SRP is standard reduction potential (left to right)
• Higher SRP means it preferentially reduce than the half-reaction with lower SRP.
• right to left is SOP (standard oxidation potential)

SOP: SRP in reverse §

• Ecell = Ered + Eoxd
• turn chemical potential energy into electrical energy when two systems react.
• driving force of a redox reaction is because it is energetically favourable to happen.
  • occurs spontaneously
    • (no energy input)
• if Ecell is positive, then reaction occurs spontaneously.
• Look at half equation thing at back of data booklet.

Electrochemical cells §

• device that transforms energy between chemical potential energy and electrical energy: two types Galvanic and Electrolytic
• galvanic are electrochemical (converts chemical potential energy into electrical energy)
  • multiple galvanic cells are connected in series we form a battery.
• electrolytic cells are electrochemical cells convert electrical energy into chemical potential energy.

galvanic cell definition §

1. a type of electrochemical cell that transforms chemical potential energy into electrical energy
2. In a spontaneous redox reaction that produces a voltage (potential difference)
3. That drives an electrical current.

setup galvanic cells §

• electrons takes path of least resistance.
  • physically separating the oxidant and reductant into “half-cells”
• electrons are forced to flow through external circuit.
• need voltmeter measuring electrical potential - called the external wire.
  • measures flow of electrons. (LABEL THIS)
  • anode and cathode
• both half cells are called electrodes
  • because electrons flow in and out of the thingy
  • electrodes have to be conductive
• electrolytes should be 1molL^-1 (because thats what standard reduction potential is measured at)
• electrons flow from anode to cathode.
• anode a negative charge and cathode a positive charge (?)
• stores some reagents, allows flow of charge within the cell.

external circuit §

• a conductor is joining the 2 electrodes
• forces electrons to flow through external circuit.
• provides pathway for electrons to flow through without cathode/anode touching.

setup idkidkidkidk §

• electrons come out of the anode -> go to cathode turning it into silver solvent.
• electrons are moving from anode to cathode IF the salt bridge didn’t exist, the cathode would become negative and anode becomes positive, but salt bridge balances the charge
• if cathode became way too negative, it would repel the electrons away and reverse the reaction Idk. if the anode was very very positive, it keeps electrons to itself.
• salt bridge keeps cells fairly neutral.
• anions negative idk.
• salt bridge is non-reactive electrolyte solution.
• potassium nitrate or sodium nitrate good salt bridges i think.
• anode is ASSIGNED positive charge - describes behaviour of electrons.
• electrons are coming towards it, cathode attracts electrons, so we assign it a positive charge - because it is attracting an opposite, negative charge.

galvanic cells summary tldr §

• at anode, material oxidised and electrons are liberated.
• the electrons flow through the external circuit towards the cathode
• at cathode, material is reduced (gains these e-)
• due to electron transfer, electrodes gain slight charge so:
  • cations flow to the cathode via salt bridge
  • anions flow to the anode via salt bridge
• prevents charge accumulation and completes the circuit
• chemical potential energy is converted to electrical energy
• overtime reagents used and concentration decreases
  • rate of redox reaction decreases
  • causes the current (n electrons flower/unit time) to decrease and voltage is prop to current, voltage delivered decreases as cell discharges
  • hence why battery becomes “weak” as they discharge.
• $\text{rate of reaction }\propto \text{ no of electrons produced -> no of electrons flowing through external wire}$

may be question on condensed galvanic cell notation

1. galvanic half cells are represented as two couples: oxidised and reduced.
2. couples are separated by a salt bridge represented by ||
3. oxidised couple is placed before reduced couple
4. single line ’|’ separates components of the couple. within, the reactant is placed first

salt bridge galvanic cells §

• salt bridge completes circuit by distributing the charge.
• connects the two half cells together, the cations flow to anode, and anions flow to cathode.
  • this occurs because the electrons go form anode to cathode, and cathode builds up negative charge (if there is no salt bridge)
  • the salt bridge lets the cations go to the positive side (anode) and anions flow to negative side (cathode) to balance the charges.
  • very cool.