20 electrode potentials and electrochemical cells
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what is a half cell/electrode?
strip of metal dipped into solution of its own ions
what does the basis of a half cell establish?
equilibrium
write an equilibrium equation for a copper half cell
Cu <-> Cu2+ + 2e-
where does the equilibrium of a half cell take place?
on the surface of the solid metal
how is a potential difference established in a half cell?
the solution has a positive charge due to the ions the metal strip has a negative charge due to the electrons collected
what is another word for potential difference?
voltage
what is another word for voltage?
potential difference
if there is a large voltage in a half cell, where does equilibrium lie?
to the right
if there is a small voltage in a half cell, where does equilibrium lie?
to the left
to connect two half cells, what are the metal strips attached by?
high resistance voltmeter
to connect two half cells, what is the solution attached by?
salt bridge
what is a salt bridge made of?
glass tube or porous solution soaked in potassium nitrate
why is potassium nitrate a suitable solution for a salt bridge?
KNO3 is unreactive with the electrodes AND the ions are free to move
why might the current produced by a cell fall to zero after some time?
all reactants used up
what will happen to a cell once the reactants are used up?
stops working OR starts to leak