electrode potentials Flashcards
1
Q
what do simple half cells consist of?
A
- a metal that acts as an electrode
- a solution of a compound containing that metal
2
Q
how many half cells does a cell have?
A
- two half cells
3
Q
how do the half cells have to be connected
A
- via a salt bridge
4
Q
why does a voltage form when you connect the two half cells into a circuit?
A
- one half cell will have more of a tendency to oxidise
- more electrons will build up, creating a potential difference between the two electrodes
5
Q
why do we need to use a high resistance voltmeter?
A
- to stop current from flowing in the circuit
- to measure maximum possible E
6
Q
how does the salt bridge work?
A
- 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
7
Q
why is a wire not used in the circuit?
A
- a metal wire would set up its own electrode system with the solutions
8
Q
what are the specific rules for conventional cell representation?
A
- 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
9
Q
for systems that do not include metals what happens?
A
- 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
10
Q
what can standard electrode potentials be used for
A
- to predict reaction feasibility under standard conditions
11
Q
how can we predict feasibility
A
- 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
12
Q
if a reaction is feasible, what will the E0 value be
A
positive
13
Q
what are batteries
A
- electrochemical cells that come in 2 main forms
14
Q
give properties of rechargeable batteries
A
- expensive
- reversible and can last longer in the long term
15
Q
what are lithium batteries used in
A
- power tools
- tablets
- mobile phones
