Electrode Potential & Electrochemical Cells Flashcards
what is a half cell
’ one half of a electrochemical cell’
how are 2 half cells connected
a salt bridge
what reaction occurs in electrochemical cells
REDOX
What does the voltmeter do
measure voltage, EMF or Ecell
electrons flow from a —— metal to a ——- ractive one
more
less
purpose of the salt bridge and what is ir
usually potassium nitrate
it is to connect the circuit, free moving ions conduct the charge
unreactive with the electrode and electrode solution
why is a wire not used
because the metal witr would set up its own electrode system with the solutions
what happens if we have a half cell with 2 aqueous ions
we must use an inert but electrically conductive electrode, platinum
electrode potential
how easily the half cell is oxidised
NO pRoblem
negative half cell - oxidation (no)
positive half cell - reduction (pr)
the standard hydrogen electrode
reference to measure standard electrode potential
0.00v
SHE standard conditions
- hydrogen gas at a pressure of 100kpa
- solution containing the hydrogen ion at 1.0 mol dm3
- temperature at 298K
- platinum electrode
standard conditions in electrode potential
- all ion solutions at 1 mol dm3
- temperature at 298K
- gasses at 100kpa
- no current flowing
what is the electrochemical series
list of half cell reactions and their standard electrode potentials
most positive is the reducing or oxidising agent
reducing
most negative is the reducing or oxidising agent
oxidising
what is the standard cell electrode potential formula
E0 = E0 REDUCED - E0 OXIDISED
‘redox’
standard cell notation
r | o || o | r
solid single lines show
solid double line
physical state change (s) to (aq)
salt bridge
systems which include 2 aqueous ions
seperate the 2 ions with a comma, because they have the same physical state.
pt (s) is also added
what is the emf of a cell
e0 cell = e0right - e0left
electrochemical cells can be used as a commercial source of electrical energy which includes,
non rechargeable
rechargeable
fuel cells
benefits using
1. cells
2. non rechargeable
3. rechargeable
4. hydrogen fuel cells
1.portable source of electrical energy
2. cheap
3. less waste, cheaper, lower environment impact
4. only waste is water, efficient, don’t need to be recharged
risks using
1. cells
2. non rechargeable
3. rechargeable
4. hydrogen fuel cells
- waste issues
- waste issues
- waste issues at end of life
- constant supply of fuels needed
hydrogen is flammable and explosive, usually made using fossil fuels
very high costs
reactions of lithium cells and alkaline hydrogen fuel cells
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