Redox II Flashcards
why do electrochemical cells use redox reaction
the electron transfer between products creates a flow of electrons.
what is the flow of charged particles called
an electrical current that flows between electrodes in the cell
what do most electrochemical cell consist of
two solutions, metal electrodes and a salt bridge
what is a salt bridge
a tube of unreactive ions that move between solutions to carry the flow of charge
what does each half cell have
cell potential which indicate how it will react
What is SHE
measuring standard for half cell potential as it has a cell potential of 0.00v
what are cell potentials measured compared to
to SHE under standard conditions
what does positive potential mean
substance more easily reduced and will gain electrons
what does negative potential mean
substance more easily oxidised and lose electrons become more stable
what are the standard conditions
solutions of 1.0mol dm-3 conc
a temperature of 298k
100 kPa pressure
what does a cell consists
HCl, Hydrogen gas, platinum electrodes
why are plantium electrodes used
metallic, so conduct electricity, but inert so doesn’t interfere with reaction
how should you represent cell in simplified way
The half-cell with the most negative potential goes on the left.
The most oxidised species from each half-cell goes next to the salt bridge.
A salt bridge is shown using a double line.
State symbols are always included.
How do you calculate Emf
E(right) - E(left)
most positive potential minus the most negative potential
what does it mean if overall cell potential is positive
more spontaneous and favourable
what does increasing concentration do to emf
what does increasing pressure do to emf
more positive as fewer electrons are produced
more negative as more electrons are produced
limitations of using SHE is
does not take kinetics into account
may be feasible but occur at such a slow rate that doesn’t even occur.
what do electrode potentials that are very positive mean
better oxidising agents
when is a disproportionation reaction feasible
overall E(cell) is positive
what does a fuel undergo in fuel cells
combustion in oxygen and energy released generate a voltage
what does hydrogen fuel cells do
uses continuous supply of hydrogen and oxygen from air to generate a continuous current
waste product of hydrogen fuel cell
water so environmentally friendly
downside of hydrogen fuel cell
high flammability of hydrogen and expensive to produce
why do negative standard electrode potentials exist use mg as an example
magnesium atoms in metal will lose electrons and break away into the solution as Mg2+
the electrons will be left behind on magnesium giving it a negative charge attracting magnesium ions from solution to recombine with electrons and re form magnesium atoms. Mg is reactive so leave excess electrons
equilibrium reached
what does a very positive electrode potential value suggest
very good reducing agent as release electrons readily
