electrochemistry and cells
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standard conditions for measuring electrode potential (3)
• conc. of solutions = 1.0 mol/dm3 • 298K • 100kpa / 1atm
standard cell for comparison (primary) - electrode used
hydrogen cell - platinum
metal dipping into solution =
half cell
if eq. lies to the left, charge will be … due to … making the potential …
negative due to build up of electrons on metal negative
if eq. lies to the right, charge will be … due to … making the potential … ??
positive as electrons used up to form the metal positive
more reactive metals tend to have ….. potentials
negative
positive potential = … hand electrode = ….
right cathode
emf of cell =
E right - E left
secondary standard
one which has been calibrated against primary standard
anode…
oxidation negative
which way do reduction reactions go
left to right
which what type of reaction is the more negative V
oxidation
which way do oxidation reactions go
right to left
what is always needed for fuel cells? - what can be used?
• oxygen!! - hydrogen/alternatives
set up used to investigate potential of an electrode
• use standard hydrogen electrode - salt bridge - potassium nitrate
for a positive potential difference, electrons moe from…. to …
left right
zinc-carbon cell - features
• cheap • non-rechargable • fairly short life
alkaline cell features
• higher cost then zinc-carbon - longer life “
lithium ion cell features
• rechargable - used in phones, computers etc.
lead acid battery features
• made of 6 cells - used in cars
how are fuel cells different to other cells?
continuous supply of chemicals into the cell, so neither run out or need recharging
fuel =
something that reacts with oxygen to release energy
most common methods of producing H2
• electrolysis of sea water - methane + steam
benefits of hydrogen-oxygen fuel cells (3)
• only waste product is H2O • efficient • dot need recharging