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chemistry - physical > electrochemical cells > Flashcards

electrochemical cells Flashcards

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1
Q

how is a potential difference produced?

A

by the flow of electrons between electrodes in the cell

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2
Q

what do electrochemical cells consist of?

A

two solutions with metal electrodes and a salt bridge

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3
Q

what does the salt bridge consist of and why?

A

unreactive ions so they can move between the solutions and carry the charge, but not interfere with the reactions

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4
Q

what half cell goes on the right?

A

the reduction – the most positive

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5
Q

what half cell goes on the left?

A

the oxidation – the most negativewh

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6
Q

what species go closest to the salt bridge?

A

the most oxidised species

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7
Q

how is the salt bridge represented?

A

two double vertical lines

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8
Q

what is the potential difference or the standard hydrogen electrode?

A

0.00V

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9
Q

what are the standard conditions of the standard hydrogen electrode?

A

298k temperature
1.00 mol dm-3 concentration of ion solutions
100kPa pressure

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10
Q

what is the electrode usually made of if there is no electrode already present?

A

platinum

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11
Q

what does a negative potential difference show?

A

the species are the best REDUCING AGENTS so are easily oxidised
the species will lose electrons

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12
Q

what does a positive potential difference show?

A

the species are the best OXIDISING AGENTS so are easily reduced
the species will gain electrons

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13
Q

how do you calculate a cells emf?

A

emf = Eright - Eleft

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14
Q

what will increasing the concentration of the solutions do to the cell emf?

A

make it more positive as fewer electrons are produced in the reaction

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15
Q

what will increasing the pressure do to the cells emf?

A

make it more negative as more electrons are produced

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16
Q

what is an example of a rechargable battery?

A

lithium ion cells

17
Q

what does a lithium ion cell consist of?

A

lithium cobalt oxide electrode and a graphite electrode

18
Q

what can a salt bridge be?

A
  • a piece of filter paper soaked in a solution of unreactive ions
  • a tube containing unreactive ions in an agar gel
19
Q

why is a high resistance voltmeter used?

A

so there is no current

20
Q

what electrode is the anode?

A

the most negative
where the oxidation occurs

21
Q

what electrode is the cathode?

A

the most positive
where the reduction occurs

22
Q

what is the electochemical series?

A

a list of electrode potentials in numerical order

23
Q

what are the examples of non-rechargable cells?

A

zinc-carbon
alkaline

24
Q

what are the examples of rechargeable cells?

A

lithium ion
lead-acid
nickel-cadmium

25
Q

what is the reduction equation in the lithium ion cell?

A

Li+ + CoO2 + e- –> LiCoO2

26
Q

what is the oxidation equation in the lithium ion cell?

A

Li –> Li+ + e-

27
Q

why don’t fuel cells run out?

A

they have a constant supply of chemicals to the cell

28
Q

what is the most common type of fuel cell?

A

hydrogen-oxygen fuel cell

29
Q

how does a hydrogen-oxygen fuel cell work?

A

anode - hydrogen is oxidised
electrons move between electrodes via an external wire
cathode - oxygen is reduced to water

30
Q

benefits of using re-chargeable cells?

A

less waste , cheaper in the long run , low environmental impact

31
Q

benefits of hydrogen fuel cell?

A

only waste product is water , don’t need recharging , very efficient

32
Q

risks of re-chargeable cells?

A

some waste issues at the end of its life

33
Q

risks of hydrogen fuel cells?

A

need constant supply of fuels , hydrogen is flammable and explosive

34
Q

explain how a salt bridge provides an electrical connection between the two solutions?

A

allows ions to flow between the solutions

35
Q
A

chemistry - physical (10 decks)

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