Electrode potentials Flashcards
Standard hydrogen electrode
diagram and conditions
100KPa
298K
What metal do you use in half cells when no metal solid is in the equation and why?
Platinum
because it is inert
conducts electricity
Features of a cell (4)
Voltmeter- Measures potential pushing power of electrons though the circuit but keeps the current at 0
Wire- Allows the movement of electrons
Electrodes- Where the half equations take place (half-cells)
Salt bridge- Filter paper soaked in KNO3, this completes the circuit and allows for the movement of ions to compensate concentration change in the half-cells
KNO3 is suitable because it doesn’t react with ions in solution
How to measure potential of an electrode
can’t measure a half-cell on its own
connect to a cell of known potential and find the difference
here you can tell if it is positive or negative
risks of using cells
Cells- waste
H fuel- needs constantly to be fuelled
Hydrogen is flammable and explosive
hydrogen usually from fossil fuels
high cost of fuel cells
benefits of using cells
portable source of electrical energy
non rechargeable is cheap
rechargeable less waste, cheaper in the long run and has a lower environmental impact
h fuel cells- only waste is water, no recharging and is very efficient
rechargeable batteries
current can be forced back in the opposite direction
dont decompose
half equations are reversed
porous separator allows the movement of ions
how to remember what happens when concentration changes to electrode potential value
forward shift (Right shift)
going forward is positive
electrode potential increases
Cu2+,+2e-,<->Cu+ E=o.15
what happens if the concentration of Cu2+ is raised
equilibrium opposes the increase in concentration so shifts right the decrease the concentration of Cu2+
equilibrium shows greater potential to gain electrons so less free electrons
electrode potential is more positive
electrode cell calculations
electrode=E,reduction-E,oxidation
