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Chemistry (Tara) > Electrochemistry > Flashcards

Electrochemistry Flashcards

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1
Q

How do you measure reactivity?

A

by how easily elements lose electrons or are oxidised

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2
Q

Electrode Potential Definition

A

the electrode potential of a metal is a measurement of the tendency of a metal to lose electrons i.e the ability to be oxidised

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3
Q

how would you measure Electrode Potential

A

using a voltaic cell

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4
Q

what does a voltaic cell do?

A

a voltaic cell uses a spontaneous chemical reaction to generate electric current

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5
Q

if 2 different metals e.g. copper and zinc are immersed in an electrolyte e.g. a dissolved sulfate salt, what happens?

A

one metal is oxidised and one metal is reduced

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6
Q

electrolyte

A

a substance that can conduct electricity easily, in the molten or dissolved state, usually a salt or an ionic compound

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7
Q

oxidation of zinc (2)

A

Zn - 2e- -> Zn2+

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8
Q

reduction of copper ions (2)

A

Cu+2 +2e- -> Cu

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9
Q

what provides the electric power for the voltaic cell?

A

the difference in the oxidation potential of the two metals provides the electric power of cell, registered on the voltmeter

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10
Q

if one metal was replaced with another in a voltaic cell

A

a different voltage would be observed

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11
Q

if zinc was replaced with lead

A

the voltage would be less as lead has less of a tendency to lose electrons than zinc

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12
Q

if zinc was replaced with magnesium

A

the voltage would be higher as magnesium has a greater tendency to lose electrons than zinc

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13
Q

reference cell for chemists for measuring all electrode potentials

A

hydrogen half cell

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14
Q

hydrogen half cell

A

consists of a platinum electrode (inert) immersed in a solution of H+ ions, with hydrogen gas bubbled over the electrode

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15
Q

electrochemical series

A

a list of metals in order of their ability to lose electrons or be oxidised

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16
Q

metals at the top of the electrochemical series ( Electrode Potential)

A

highly electropositive

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17
Q

metals at the bottom of the electrochemical series (Electrode Potential)

A

less electropositive

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18
Q

metals at the top of the electrochemical series (reactivity)

A

extremely reactive

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19
Q

metals at the bottom of the electrochemical series (reactivity)

A

less reactive

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20
Q

metals at the top of the electrochemical series (stability)

A

form very stable compounds

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21
Q

metals at the bottom of the electrochemical series (stability)

A

form less stable compounds

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22
Q

metals at the top of the electrochemical series (nature)

A

not free in nature (very reactive)

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23
Q

metals at the bottom of the electrochemical series (nature)

A

can be found free in nature

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24
Q

one last thing about metals at the top of the electrochemical series

A

they will displace those lower down from a solution of their salts

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25
Q

Acronym to remember the electrochemical series

A

little polly can seldom marry a zulu in the lovely honolulu causing many strange glances

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26
Q

little

A

lithium

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27
Q

polly

A

potassium

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28
Q

can

A

calcium

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29
Q

seldom

A

sodium

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30
Q

marry

A

magnesium

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31
Q

a

A

aluminium

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32
Q

zulu

A

zinc

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33
Q

in

A

iron

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34
Q

the

A

tin

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35
Q

lovely

A

lead

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36
Q

honolulu

A

hydrogen

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37
Q

causing

A

copper

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38
Q

many

A

mercury

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39
Q

strange

A

silver

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40
Q

glances

A

gold

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41
Q

reaction between sodium and zinc chloride

metals higher up in Ec.s displace those lower down

A

2Na + ZnCl2 -> Zn + 2 NaCl

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42
Q

equation for scrap iron used to extract copper metal from a solution of its salts

A

Fe + Cu2+ -> Cu(↓) + Fe+2

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43
Q

EXPERIMENT - DISPLACEMENT REACTIONS OF METALS

Zinc in copper (II) sulfate solution

A

some pieces of zinc metal added to solution of copper sulfate
copper (reddish) metal appears on the zinc and some of the zinc dissolves
colour of copper sulfate becomes less blue

44
Q

EXPERIMENT - DISPLACEMENT REACTIONS OF METALS

magnesium in copper (II) sulfate solution

A

some pieces of magnesium were added to a solution of copper (II) sulfate
copper (reddish) appears in magnesium and some of the magnesium dissolves
solution becomes less blue in colour

45
Q

OXIDATION OF SULPHITE TO SULPHATE USING A HALOGEN SUCH AS CHLORINE WATER (OR BROMINE OR IODINE)

A

some sodium sulphite added to test tube
some chlorine water wad then added
the solution was tested for the presence of sulphate ions by added barium chloride to form a white precipitate that is insoluble by HCl

46
Q

halogens oxidise iron (II) to

A

iron (III)

47
Q

halogens are

A

oxidising agents

48
Q

of chlorine, bromine and iodine, which is the strongest oxidising agent?

A

chlorine

49
Q

COMPARING HALOGENS AS OXIDISING AGENTS

first step

A

chlorine water added to a bromide salt

50
Q

COMPARING HALOGENS AS OXIDISING AGENTS

result of first step

A

the solution turns a red/orange colour as bromine is formed

51
Q

COMPARING HALOGENS AS OXIDISING AGENTS

second step

A

chlorine water added to an iodide salt

52
Q

COMPARING HALOGENS AS OXIDISING AGENTS

result of seconds step

A

solution turns a red/brown as iodine is formed

53
Q

COMPARING HALOGENS AS OXIDISING AGENTS

third step

A

bromine water is added to an iodide salt

54
Q

COMPARING HALOGENS AS OXIDISING AGENTS

result of third step

A

solution turns a red/brown as iodine is formed

55
Q

COMPARING HALOGENS AS OXIDISING AGENTS

fourth step

A

bromine water added to chloride salt

56
Q

COMPARING HALOGENS AS OXIDISING AGENTS

result of fourth step

A

no reaction occurs, as chlorine is a stronger oxidising agent

57
Q

electrolysis definition

A

a process where an electrical current is used to bring about a chemical reaction

58
Q

electrolysis: what splits up the chemical substances

A

electricity

59
Q

electrolysis: what carries the current and why

A

an electrolyte - contains ions that are free to move

60
Q

electrolysis: how to connect to power supply

A

electrodes- inert (platinum or graphite) or metal itself

61
Q

electrolysis: where does reduction take place

A

cathode (-)

62
Q

electrolysis: where does oxidation take place

A

anode (+)

63
Q

electrolysis: as soon as current begins to flow

A

chemical changes occur

64
Q
  1. ELECTROLYSIS OF ACIDIFIED WATER USING INTERT ELECTRODES

compounds involved

A

H2O and H2SO4

65
Q
  1. ELECTROLYSIS OF ACIDIFIED WATER USING INTERT ELECTRODES

cathode, reduction equation

A

4H2O + 4e- -> 2H2 + 4OH-

66
Q
  1. ELECTROLYSIS OF ACIDIFIED WATER USING INTERT ELECTRODES

anode, oxidation equation

A

2H2O - 4e- -> O2 + 4H+

67
Q
  1. ELECTROLYSIS OF ACIDIFIED WATER USING INTERT ELECTRODES

cathode explanation

A

reduction, water molecules gain electrons, to form hydrogen gas. To test for hydrogen gas the gas is collected in a test tube and you hear a pop when lighting

68
Q
  1. ELECTROLYSIS OF ACIDIFIED WATER USING INTERT ELECTRODES

anode explanation

A

oxidation, electrons are lost from the water molecules which causes the water molecules to break down and oxygen gas is produced, to test for oxygen gas, the gas is collected in a test tube and when a glowing splint is inserted into a test tube, it relights

69
Q
  1. ELECTROLYSIS OF ACIDIFIED WATER USING INTERT ELECTRODES

overall reaction

A

2H2O -> 2H2 + O2

70
Q
  1. ELECTROLYSIS OF ACIDIFIED WATER USING INTERT ELECTRODES

ratio of H2 to O2

A

2:1

71
Q
  1. ELECTROLYSIS OF ACIDIFIED WATER USING INTERT ELECTRODES

electrolyte

A

sulfuric acid, doesn’t take part however as it is very low done in the series - not easily oxidised

72
Q
  1. ELECTROLYSIS OF ACIDIFIED WATER USING INTERT ELECTRODES

where is it carried out

A

in a Hoffman voltmeter

73
Q

2.ELECTROLYSIS OF AQUEOUS SODIUM SULPHATE USING INERT ELECTRODES AND UNIVERSAL INDICATOR
compounds involved

A

H2O and Na2SO4

74
Q

2.ELECTROLYSIS OF AQUEOUS SODIUM SULPHATE USING INERT ELECTRODES AND UNIVERSAL INDICATOR
cathode, reduction equation

A

4H2O + 4e- -> 2H2 + 4OH-

75
Q

2.ELECTROLYSIS OF AQUEOUS SODIUM SULPHATE USING INERT ELECTRODES AND UNIVERSAL INDICATOR
anode, oxidation equation

A

2H2O - 4e- -> O2 + 4H+

76
Q

2.ELECTROLYSIS OF AQUEOUS SODIUM SULPHATE USING INERT ELECTRODES AND UNIVERSAL INDICATOR
cathode explanation

A

reduction, water molecules gain electrons and hydrogen gas produced, production of hydroxide ions, area around cathode becomes alkaline - blue in universal indicator

77
Q

2.ELECTROLYSIS OF AQUEOUS SODIUM SULPHATE USING INERT ELECTRODES AND UNIVERSAL INDICATOR
anode explanation

A

oxidation, water molecules lose electrons and oxygen gas is liberated, production of hydrogen ions at anode. area around anode becomes acidic - red in universal indicator

78
Q

universal indicator in neutral solution

A

green

79
Q
  1. ELECTROLYSIS OF AQUEOUS POTASSIUM IODIDE USING INERT ELECTRODES AND PHENOLPHTHALEIN INDICATOR
    compounds involved
A

H2O and KI

80
Q
  1. ELECTROLYSIS OF AQUEOUS POTASSIUM IODIDE USING INERT ELECTRODES AND PHENOLPHTHALEIN INDICATOR
    cathode reduction equation
A

2H2O + 2e- -> H2 + 2OH-

81
Q
  1. ELECTROLYSIS OF AQUEOUS POTASSIUM IODIDE USING INERT ELECTRODES AND PHENOLPHTHALEIN INDICATOR
    anode oxidation equation
A

2I- -2e- -> I2

82
Q
  1. ELECTROLYSIS OF AQUEOUS POTASSIUM IODIDE USING INERT ELECTRODES AND PHENOLPHTHALEIN INDICATOR
    cathode explanation
A

reductio, water molecules gain electrons and hydrogen gas liberated. Build up of hydroxide ions, area around cathode alkaline, phenolphthalein indicator pink in alkaline soln, pink around cathode

83
Q
  1. ELECTROLYSIS OF AQUEOUS POTASSIUM IODIDE USING INERT ELECTRODES AND PHENOLPHTHALEIN INDICATOR
    anode explanation
A

oxidation, iodide ions are oxidised and lose electrons to form iodine as iodine is relatively high in electrochemical series, easily oxidised, red brown colour observed from I2

84
Q

electrodes for experiments 1,2 and 3

A

inert

85
Q
  1. ELECTROLYSIS OF AQUEOUS COPPER (II) SULPHATE USING COPPER ELECTRODES
    compounds involved
A

H2O and CuSO4 and Cu (electrodes)

86
Q
  1. ELECTROLYSIS OF AQUEOUS COPPER (II) SULPHATE USING COPPER ELECTRODES
    cathode, reduction equation
A

Cu2+ + 2e- -> Cu

87
Q
  1. ELECTROLYSIS OF AQUEOUS COPPER (II) SULPHATE USING COPPER ELECTRODES
    anode, oxidation equation
A

Cu - 2e- -> Cu 2+

88
Q
  1. ELECTROLYSIS OF AQUEOUS COPPER (II) SULPHATE USING COPPER ELECTRODES
    cathode explanation
A

copper (II) ions from copper (II) sulphate soln. are attracted to cathode, as copper is relatively high in the electrochemical series. Reduction occurs, so the ions gain electrons to form copper metal. An increase in weight of the cathode as more copper is being deposited

89
Q
  1. ELECTROLYSIS OF AQUEOUS COPPER (II) SULPHATE USING COPPER ELECTRODES
    anode explanation
A

the copper from anode is oxidised and loses electrons to become copper (II) ions, replaces copper (II) ions lost at cathode. decrease in weight at anode as the copper is being oxidised (corroded away)

90
Q

why does copper need to be purified for industry?

A

as impurities present naturally in copper reduce its ability to conduct electricity

91
Q

PURIFICATION OF COPPER

anode

A

made of impure copper, oxidation occurs here and the copper in the impure anode loses electrons to become copper (II) ions

92
Q

PURIFICATION OF COPPER

cathode

A

made of a thin sheet of pure copper, reduction occurs here and the copper (II) ions of the electrolyte (Copper (II) sulphate) gain electrons to form copper metal
the copper metal is pure and is deposited on the cathode

93
Q

PURIFICATION OF COPPER

what happens to the impurities

A

they fall to the bottom of the apparatus

these are valuable as the contain gold

94
Q

covering a nickel spoon with silver:

spoon is the

A

cathode

95
Q

covering a nickel spoon with silver:

silver is the

A

anode

96
Q

covering a nickel spoon with silver:

electrolyte

A

a silver salt

97
Q

covering a nickel spoon with silver:

anode equation

A

Ag - e- -> Ag+

98
Q

covering a nickel spoon with silver:

cathode equation

A

Ag+ +e- -> Ag

99
Q

covering a nickel spoon with silver:

quantity of silver deposited depends on 2

A

time you leave it their

quantity of electricity passed through electrolyte

100
Q

EPNS

A

electroplated nickel silver

101
Q

the object to be covered is always the

A

cathode

102
Q

handlebars o bicycles

A

plated with chromium to prevent corrosion from rain

103
Q

DEMONSTRATION OF IONIC MOVEMENT

highly coloured compound

A

copper chromate

CuCrO4

104
Q

DEMONSTRATION OF IONIC MOVEMENT

Cu2+ colour

A

blue

105
Q

DEMONSTRATION OF IONIC MOVEMENT

CrO4 2- colour

A

orange due to chromium with valency +6

106
Q

DEMONSTRATION OF IONIC MOVEMENT

set up experiment

A

soak a piece of filter paper with some salt solution, so that it can conduct electricity, and then place some copper chromate crystals on the filter paper and connect it to an electric supply

107
Q

DEMONSTRATION OF IONIC MOVEMENT

observation

A

blue Cu2+ ions will be attracted to cathode and orange CrO4 2- ions will be attracted to the anode - demonstrating ionic movement

Chemistry (Tara) (50 decks)

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