Redox 2 Flashcards
Standard electrode potential
Potential difference measured when half-cell connected to a standard hydrogen electrode under standard conditions (298K, 100kPa, 1M solutions)
Standard hydrogen electrode drawing
Look it up
Standard conditions
298K, 100kPa, 1M solutions
Why is reference electrode necessary
Because voltage is relative value so hydrogen chosen as arbitrary reference.
E cell of hydrogen electrode
0.00V
When use platinum electrode
When not metal and its ion
How to calculate E cell value
Keep E value of reduced, flip value of oxidised and add.
+ve E cell meaning
Feasible
How to write E cell diagram
Oxidation on left, reduction on right
Why are conditions important when measuring E cell
Each half cell is at equilibrium therefore changing conditions shifts equilibrium. The more electrons are released, the more negative the solution
Why does +ve E cell mean feasible
Because it is proportional to S total, which is proportional to lnK.
How to tell if an ion is stable wrt other ions
See if disproportionation is feasible.
Types of cells
Non-rechargeable, rechargeable and fuel cell
Methanol fuel cells half reactions (acidic electrolyte)
CH3OH + H2O -> CO2 + 6H+ + 6e- at anode (oxidation)
O2 + 4H+ + 4e- -> 2H2O at cathode (reduction)
Platinum catalyst for both reactions
Acid hydrogen fuel cell half reactions
H2 -> 2H+ + 2e- at anode (oxidation)
O2 + 4H+ + 4e- -> 2H2O at cathode (reduction)
