Electrode potentials Flashcards
(23 cards)
Salt bridge
allows movement of ions
what’s salt bridge soaked in?
KNO3 because it doesn’t react with any ions in the solution
standard conditions
100kPa 298K 1moldm-3
electrode potential of cell
reduction - oxidation
negative electrode
oxidised
positive electron
reduced
more negative electrode potential
best reducing agent
more positive electrode potential
best oxidising agent
Voltmeter
measures potential pushing power of electrons through circuits but keeps current 0
feasible reaction
positive Eø
half equations always show
reduction
right hand side
reduction
hydrogen fuel cell
continuous supply of chemicals so neither run out
hydrogen-oxygen fuel cell
2 Pt electrodes separated by a special polymer electrolyte which allows ions to pass through
standard hydrogen electrode always on
left
risks and benefits of hydrogen fuel cell
risks- H2 flammable, made with fossil fuels, high cost
benefits- only waste product is water, very efficient, no re charging needed
rechargeable cell
electrons can be forced back the opposite direction by an applied external current. Half cell equations are reversed, electrodes designed so they don’t decompose
lithium ion batteries
light weight metal gives a light weight small battery, electrolyte phase is a polymer so won’t leak
non-rechargeable cells
chemicals used up over time and EMF drops, once completely used up cell is flat EMF 0v
Daniell cell
Zn/Cu cell Zn electrode over time starts to run out
Zn/Carbon cells
Zn is -ve electrode and acts as a case and has a paste electrolyte solution. Carbon is +ve electrode and is a rod down the centre of the canister (behaves like Pt)
Often leaks after being used for a long time as Zn oxidised to Zn2+ which wears the case away
non-reactive porous separator is to allow movement of ions
Equilibrium shift to right
more +ve, going away from electrons
equilibrium shift left
more -ve, going towards electrons
