1.11 Electrode Potentials Flashcards
why does a voltage form across two half cells?
- one half cell has a greater tendency to oxidise an ion and release electrons than the other
- more electrons will build up on one electrode
- creating a potential difference between the electrodes
why do we use a high resistance voltmeter?
- to stop current from flowing in the circuit
what is the salt bridge?
- connects the circuit
- should be unreactive with electrodes and electrode solution
- made from a piece of paper soaked in a salt solution
what happens to the most positive electrode
- reduction, ions accept electrons
what happens to the more negative electrode
- oxidiation, electrons are given off
how does cell notation work?
- write both reduction equations for the elements
- determine which undergoes oxidation/reduction
- starting from left of cell, write the oxidation equation, then the reduction
- seperate with a salt bridge
what happens if a system doesnt inclue a metal?
- use a platinum electrode
why do we use a platinum electrode?
- inert
- provides conducting surface for electron transfer
- electrically conductive
what is the standard hydrogen electrode used for?
- measures potential of all electrodes by comparing them to SHE
- SHE is assigned e potential of 0V
what are the standard conditions required?
298K
100kPa
both ion solutions have to have a concentration of 1moldm^-3
what will happen to the electrode potential if hydrogen ion concentration is reduced
2H+ + 2e > H2
- reducing H+ concentration causes equilibrium to shift to the left to reduce this change
- this will cause electrode potential to become more negative
what is the equation for electrode potential?
E reduced - Eoxidised = Ecell
give the oxygen electrode equation for ethanol fuel cells
O2 + 4H+ + 4e- > 2H2O
give the ethanol electrode equation for ethanol fuel cells
C2H5OH+ 3H2O > 2CO2 + 12H+ + 12e
why can ethanol be considered to be a carbon neutral fuel?
- ethanol can be made from renewable resources in a carbon neutral way
- absorbed in photosynthesis, released by combustion etc
give the equation for the oxygen electrode and hydrogen electrode at hydrogen fuel cells
O2 + 2H2O + 4e > 4OH-
H2 + 2OH- > 2H2O + 2e
what are some advantages of using ethanol fuel cells?
- less pollution and no CO2 emission
- greater efficiency
