ELECTRODE POTENTIAL Flashcards
Half cell
a half cell is one half of an electrochemical cell. they can be constructed of a metal dipped in its own ion or a platinum electrode in 2+ aqueous ions.
why do we use platinum electrode
because it is inert and electrically conductive metal.
electrochemical cells
electrochemical cells are made up of two half cells joined together by a wire, a voltmeter and a salt bridge. there are always two reaction occuring oxidation and reduction therefore it is a redox reaction.
what is a salt bridge
strip of a filter paper soaked in kno3 solution.
how do electrons flow between half cells
always from a high recating metal to the lower one.
example zinc gets oxidised and gets thinner whereas copper gets reduced and becomes thicker.
electrode potential or delta e
each half cell has its own electrode potential. it tells us how easily the half cell gives up electrons ( becomes oxidised)
how do we write up the equations
always in reduced form. never in oxidised form.n
acronym we use
NO PROBLEM
the most negative value is oxidised meaning that equation needs to be flipped
and the most positive value is the one getting reduced.
SHE stands for?
STANDARD HYDROGEN ELECTRODE
SHE ( STANDARD HYDROGEN ELECTRODE)
SHE is a reference for measuring standard electrode potential.
value of SHE
0.00VOLTS
What affects the value of an electrode potential
temperarure, pressure and concentration
standard conditions?
temperature – 298K
Pressure – 100Kpa
concentration– 1mol per dm -3.
note
when we say concentration we actually mean, 1 mol dm-3 of H+ ion not actually acid. if we use h2so4, then we use 0.5 mol dm-3 since its a diprotic acid.
electro chemical series
electro chemical series is a list of half cell reactions and their standard electrode potentials.
oxidisation and oxiding agent
oxifdation is losing electron and oxidising agent is gaining electron
reduction ans reducing agent
reduction is gaining electron and reducing agent is losing electron
note for electro chemical series
in an electro chemical series, we always find the oxidising agent in the left hand side and the reducing agent always on the right hand side.
standard cell potential
e reduced - e oxidised.
cell notation
standard way of representing cells in chemistry.
cell notation format
reduced form l oxidised form ll oxidised form l reduced form
where ll represents a salt bridge
and l represents a physical state change.
what do we do if we have two aqueous ions
we use a comma
batteries
batteries are electro chemical cells that exists in two forms : rechargeable and non rechargeable.
example of rechargeable battery
lithium ion batteries used in phone etc.
