unit 4 section 3 electrode potentials and cells Flashcards
describe an electrochemical cell
two different metals are dipped in salt solutions of their own ions and is connected by a wire. there is also a salt bridge which allows the free flow of electrons from one cell to another.
explain the movement of electrons in an electrochemical reaction
the electrons flow the wire from the more reactive metal to the least reactive metal.
what is the cell potential or the EMF
it is the difference between the voltages of the two half cells.
the voltages can be measured with a voltmeter in the external circuit
what is electrode potentials
it is the measure of how easily a metal is oxidised
- metal that is easily oxidised has a more negative electrode potentials
- while metals that are harder to oxidise will have a less negative or more positive electrode potential.
what is the conventional representation and how it is done
it is the shorthand way of drawing/representing electrochemical cells.
- the oxidised forms and the reduced forms of each species of each half-cell and then arrange them in a row.
Zn | Zn2+ || Cu2+ | Cu
the || represents the salt bridge
what is the equation for the electrode potential
E(cell) = E(right hand side) - E(left hand side)
or
E(cell) = E(reduced) -E(oxidised)
what factors affect the electrode potential
since the half cell reaction is reversible, factors such as concentration, temperature and pressure affects the position of the equilibrium which affects the electrode potential.
how can the factors that affect the electrode potential be overcome
they use standard conditions . this means you always getting the same value for the electrode potential and you can compare values for different cells.
what is the standard hydrogen electrode
it is used as a reference to measure the standard electrode potentials. in the standard hydrogen electrode, hydrogen gas is bubbled through a solution of aqueous H+ ions.
what is an electrochemical series
it is a big list of electrode potential for different electrochemical half-cells
what is the equation for the electrode potential when you are given the electrochemical series
E(cell) = E(reduced) - E(oxidised)
what type of reactions occurs in a non rechargeable battery and what is the common type of cell
they use irreversible reactions, a common type of non rechargeable cell is a dry alkaline battery.
what types of reaction does rechargeable batteries use
they use reversible reactions
what are the two types of rechargeable reaction
NiCad( nickel-cadmium ) and lead-acid.
explain how a rechargeable batteries work
to recharge the batteries, a current is supplied to force electrons to flow in the opposite direction around the circuit and reverse the reactions. this is possible because none of the substances in the rechargeable reaction are used up or lost.
