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chem ! > electrolysis ! > Flashcards

electrolysis ! Flashcards

1
Q

electrolysis !

A

conduction of electricity by an ionic compound (electrolyte) when molten or dissolved in water, leading to the decomposition of the electrolyte

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2
Q

parts of electrolytic cell !

A

electrode
anode
cathode
battery

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3
Q

electrolyte !

A

ionic compound

when in molten state : mobile ions conduct electricity

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4
Q

electrode !

A

electrical conductor (carbon, graphite)

connected to positive & negative terminals of battery

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5
Q

anode !

A

positive electrode : connected to positive terminal of battery

electrons leave electrolyte

oxidation occurs : lose electrons

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6
Q

cathode !

A

negative electrode : connected to negative terminal of battery

electrons enter electrolyte

reduction occurs : gain electrons

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7
Q

battery !

A

elects pump : draws electrons away from anode

  • electrons : enter positive terminal of battery & pumped out at negative terminal
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8
Q

external circuit !

A

conducts electricity due to flow of electrons

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9
Q

factors affecting selective discharge of ions !

A

position of metal / ion in reactivity series

  • selective discharge of cations at cathode
  • selective discharge of anions at anode

concentration of selective discharge at anions

nature of electrode

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10
Q

selective discharge of cations at cathode

A

metal/hydrogen : formed at cathode

ions of more reactive metals : remain in solution as ions -> not discharged as they are more stable as ions

ions of less reactive metals : preferentially discharged -> reduced back to metal as they are less stable in solution

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11
Q

selective discharge of anions at anode !

A

non-metals (excluding H) : formed at anode

ions higher in series : remain in solution as they are more stable in solution

ions lower in series : preferentially discharged as they are less stable in solution

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12
Q

cathode reactive series !

A 
SO4 2- 
NO3- 
CL- 
BR-
I-
OH-
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13
Q

concentration of selective discharge of anions !

A

high concentration of ion : more readily discharged

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14
Q

nature of electrode !

A

product of electrolysis : differ when diff electrodes are used
- eg : inert -> carbon, platinum

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15
Q

applications of electrolysis !

A

electrolytic purification of copper

electroplating

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16
Q

electrolytic purification of copper !

A

anode : impure copper
- Cu (s) -> Cu2+ (aq) + 2e-

cathode : pure copper
- Cu2+ (a1) +2e- -> Cu (s)

circuit closed : pure copper from anode dissolves -> form Cu2+ ions -> move over to cathode

impurities (silver,platinum) : fall to bottom of anode

mass of anode decreases, mass of cathode increases

17
Q

electroplating !

A

process of depositing a layer of metal on another substance by electrolysis

anode : source of plating metal
cathode : object to be electroplated
electrolyte : aq solution of a salt of the plating metal

18
Q

electroplating uses !

A

prevent objects from corrosion

give the object a shiny/attractive appearance

19
Q

electroplating conditions !

A

metal object to be plated : must be clear & free of grease

concentration of metal ions : must be low

electric current : must not be too large
- coating layer will form too rapidly & peel off easily

20
Q

simple cells !

A

device that converts chemical energy into electrical energy

made by placing 2 diff metals which act as the electrodes in contact with an electrolyte

anode : more reactive metal -> gives up electrons to form ions -> oxidation occurs

cathode : less reactive metal -> ions in solution gains electrons -> reduction occurs

electron flow from more reactive metal (anode) to the less reactive metal (cathode)

21
Q

simple cells & reactivity series !

A

the further apart the 2 metals are in the reactivity series, the greater the outage produced in the cell

no current flow if electrodes are made up of the same metal

22
Q

simple cell vs electrolytic cell !

A

simple cell

  • opp of electrolytic cell in terms of energy conversions
  • converts chemical energy -> electrical energy
  • produce electricity

electrolytic cell

  • converts electrical energy -> chemical energy
  • uses electricity

similarity : both are electrochemical cells

23
Q

advantages of using hydrogen as fuel!

A

does not cause pollution : product of combustion of water

renewable source of energy : source of H is the electrolysis of water

efficient source of energy : releases twice the amt of energy compared to other fuels

24
Q

disadvantages of using hydrogen as fuel !

A

no cheap source of hydrogen : obtaining it from electrolysis is expensive

extremely flammable & explosive : special care & precaution required

is a gas & very light : requires larger storage volume compared to other fuels

chem ! (5 decks)

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