electrode potentials Flashcards
what do simple half cells consist of?
- a metal that acts as an electrode
- a solution of a compound containing that metal
how many half cells does a cell have?
- two half cells
how do the half cells have to be connected
- via a salt bridge
why does a voltage form when you connect the two half cells into a circuit?
- one half cell will have more of a tendency to oxidise
- more electrons will build up, creating a potential difference between the two electrodes
why do we need to use a high resistance voltmeter?
- to stop current from flowing in the circuit
- to measure maximum possible E
how does the salt bridge work?
- usually made from a piece of filter paper soaked in a salt solution
- salt should be unreactive with the electrodes and electrode solution
- used to connect the circuit
why is a wire not used in the circuit?
- a metal wire would set up its own electrode system with the solutions
what are the specific rules for conventional cell representation?
- the half cell with 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
- always include state symbols
for systems that do not include metals what happens?
- a platinum electrode must be used and included in the cell diagram
- it provides a conducting surface for electron transfer
- it is unreactive and can conduct electricity
what can standard electrode potentials be used for
- to predict reaction feasibility under standard conditions
how can we predict feasibility
- identify which is being oxidised with most negative E value
- take the oxidised equation and reverse it
- combine these 2 equations to form the feasible reaction
- compare with question to see
if a reaction is feasible, what will the E0 value be
positive
what are batteries
- electrochemical cells that come in 2 main forms
give properties of rechargeable batteries
- expensive
- reversible and can last longer in the long term
what are lithium batteries used in
- power tools
- tablets
- mobile phones
what components do mobile phones have with a lithium ion cell
- Electrode A - lithium cobalt oxide
- Electrode B - graphite
- Electrolyte - lithium salt dissolved in an organic solvent
what is the electrolyte
- part of battery that acts as a conductive pathway for ions to move from one electrode to another
what does the negative electrode inside a battery do
- produces electrons
how do rechargeable batteries work
- plugging them into supply a current
- current forces electrons to flow in opposite way
- reverse the overall discharge equation to show a battery recharging
