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Chemistry GCSE > Topic 5 - Electrolysis, Metals and Extraction, Transition Metals > Flashcards

Topic 5 - Electrolysis, Metals and Extraction, Transition Metals Flashcards

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1
Q

electrolysis

A

using electricity to brake down substances (decompose electrolytes)
-> separate the elements in insoluble ionic compounds

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2
Q

electrolyte

A

liquid or solution that contains an ionic compound - ions are free to move - they can conduct electricity

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3
Q

cations

A

positive ions

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4
Q

anions

A

negative ions

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5
Q

cathode

A

negative electrode

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6
Q

anode

A

positive electrode

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7
Q

electrodes in electrolysis

A

solid conductors that are immersed in an electrolyte and are connected to a direct current electricity supply to drive a chemical reaction
-> ions are attracted to the two electrons

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8
Q

what are cations attracted to

A

negative cathode

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9
Q

what are anions attracted to

A

positive anode

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10
Q

what happens to the ions at the anode (MOLTEN ELECTROLYSIS)

A
  • get discharged
  • the negative ions loose electrons - become a neutral atom
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11
Q

what happens to the ions at the cathode (MOLTEN ELECTROLYSIS)

A
  • get discharged
  • the electrons are transferred from the electrode to the positive ions - make a pure neutral molecule
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12
Q

oxidation is..

A

Loss of electrons

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13
Q

Reduction is..

A

Gain of electrons

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14
Q

OILRIG stand for

A

Oxidation Is Loss of electrons
Reduction Is Gain of electrons

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15
Q

where does reduction take place

A

Cathode

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16
Q

Where does oxidation take place

A

Anode

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17
Q

what do ions turn into after being at the cathode

A

atoms

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18
Q

what do ions at the anode turn into

A

molecules

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19
Q

cathode half equation (reduction)

A
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20
Q

anode half equation (oxidation)

A
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21
Q

what type of electrode is used when doing molten electrolysis

A

an inert (unreactive) electrode

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22
Q

in the electrolysis of a MOLTEN salt what is usually formed at the cathode

A

metal

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23
Q

in the electrolysis of a MOLTEN salt what is usually formed at the anode

A

non-metal

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24
Q

what is attracted and formed at the cathode in AQUEOUS electrolysis

A
  • attracted: the cations and the H+ ions
  • formed: if the metal is less reactive than hydrogen, the metal is discharged (formed), if the hydrogen is more reactive than the metal, hydrogen is formed
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25
Q

what is attracted and forms to the anode in the AQUEOUS electrolysis

A
  • attracted: anions and OH- ions
  • formed: the simplest ion
    -> if it is easier to discharge (get rid of the electrons in the outer shell) the non-metal, the non-metal ion will be formed but if it’s easier to discharge oxygen, oxygen is formed
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26
Q

in a AQUEOUS solution what gets formed at the cathode and anode

A

water decomposes to form…
cathode - hydrogen gas
anode - oxygen gas

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27
Q

where do the electrons go after being transferred to the cathode (MOLTEN ELECTROLYSIS)

A

they go round the circuit to the anode where the anode gives the electrons to the anion there

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28
Q

reactivity series

A

a list of metals in order of increasing reactivity (most reactive at the top)

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29
Q

what metals react the most with cold water and form hydrogen and a metal hydroxide

A

potassium, sodium, calcium

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30
Q

Metals react very slowly if at all with cold water but react with steam to form hydrogen and metal oxide

A

Magnesium, aluminium, zinc, iron

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31
Q

What metals do not react with cold water or steam?

A

Copper, silver, gold

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32
Q

what are the products if metal reacts with a dilute acid

A

hydrogen and a salt solution

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33
Q

what do you say when a metal reacts with a dilute acid?

A

bubbles of gas will be seen
-> bubbles formed the more reactive metal

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34
Q

what happens to the metals atom in reaction with a dilute acid

A
  • loose electrons to form positive ions (cations)
    -> more easily a metal atom loses electrons to the higher the metal is in the reactivity series
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35
Q

displacement reaction

A

occurs when a more reactive element displace is a less reactive element from a compound that contains a less reactive element

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36
Q

spectator ions

A

ion that is present in a chemical reaction but does not participate in it
-> this ion gets removed when making an ionic equation as it doesn’t change

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37
Q

redox reaction

A

a reaction when one substance is oxidised and another is reduced

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38
Q

how are very unreactive metals found naturally

A

in the native state (as uncombined elements)

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39
Q

how are reactive metals found naturally?

A

found in compounds in rocks after they have reacted with other elements

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40
Q

Extraction

A

The process of obtaining a metal from these compounds that they are naturally found in

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41
Q

ore

A

A rock that contains enough of a compound to extract a metal for profit

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42
Q

What method is used to extract compounds of metals below carbon in the reactivity series

A

Heated with carbon and carbon is more reactive than the element so displaces it

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43
Q

If a metal is more reactive than carbon. How is it extracted?

A

Using the electrolysis of a molten compounds

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44
Q

How does electrolysis purify and what happens to the impurities?

A

The positive minds move to the negative electrode (cathode) where they gain electrons and for deposit of a pure metal
-> impurities from the anode do not form irons and collect below the anode as ‘sludge’

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45
Q

What are biological methods of metal extraction?

A
  • bioleaching
  • phytoextraction
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46
Q

bioleaching

A
  • Uses bacteria grown on a low-grade ore
  • the bacteria produce a solution containing the metal ions (leachate)
  • The metal is extracted from the Leche by displacement using a more reactive metal, then it’s purified by electrolysis
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47
Q

phytoextraction

A
  • involves growing plants that absorb metal compounds
  • Plants are burned from ash from which the metal is extracted
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48
Q

+ and - of bioleaching and phytoextraction

A
49
Q

+ and - of bioleaching and phytoextraction

A
50
Q

What has to be removed in order to obtain a metal from its oxide

A

oxygen

51
Q

what happens in metal extraction with a metal oxide - oxidisation and reduction (METAL LESS REACTIVE THAT CARBON)

A

a metal less reactive that carbon is obtained by removing oxygen from the metal oxide by heating with carbon. The metal oxide is reduced to just the metal; carbon is oxidised to carbon dioxide.
-> metal oxide + carbon -> metal + carbon dioxide

52
Q

What happens in metal extraction using electrolysis?

A
  • The metal ions attracted to the cathode where they gain electrons to form the metal
  • The oxide irons are attracted to the anode where they lose electrons to form oxygen
  • At the high temperature in the electrolysis cell the oxygen reacts with the graphite (carbon) anodes to form carbon dioxide
53
Q

when does corrosion happen

A

When a metal reacts with oxygen
-> the metal gains oxygen and so is oxidised

54
Q

rusting

A

corrosion of iron, which also requires water as well as oxygen

55
Q

what does it mean if a metal corrodes more quickly

A

it’s more reactive

56
Q

What is a metal that does not corrode at all

A

gold

57
Q

What is a metal that does not corrode but is quite reactive and why

A

aluminium because their surfaces form a protective layer (a tarnish) which prevents further reaction

58
Q

+ and - of recycling metals

A

+ Natural reserves of metal ores will last longer
+ The need to mine ores is reduced; mining can damage the landscape as well as creating noise and dust pollution
+ less pollution may be produced; for example sulfur dioxide is formed when some metals are extracted from metal sulfide ores
+ many metals need less energy to recycle them them to extract new metal from the ore
+ less waste metal ends up in landfill sites
- cost
- requires energy used in collecting transporting and sorting metals to be recycled - more energy is required to recycle than to extract the new metal

59
Q

Four stages of a life cycle assessment

A
  • manufacturing and packaging the product
  • Using the product
  • Disposal of product
  • Obtaining and processing raw materials
60
Q

life cycle assessment (LCA)

A

Carried out to work out the environmental impact of a product

61
Q

for example, why when sodium chloride solution is electrolysed, why is hydrogen produced instead of sodium?

A

Hygienist produce instead of sodium because hydrogen ions have a lower reduction potential then sodium irons making them more easily reduced at the cathode

62
Q

what metals are more reactive that hydrogen

A

potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, tin, lead

63
Q

reversible reaction

A

both forward and backward reactions occur at the same time

64
Q

symbol to show reversible reactions

A
65
Q

symbol to show reversible reactions

A
66
Q

dynamic equilibrium

A

occurs when the forward and reverse reactions rates are equal

67
Q

equilibrium

A

state in which the rate of the forward reaction equals the rate of the backward reaction - reaction comes to a halt

68
Q

where does dynamic equilibrium only occur

A

in a closed system

69
Q

why does dynamic equilibrium not occur in an open system

A

gases could escape and so equilibrium would not be achieved

70
Q

harber process

A

a important chemical reaction which is used to make ammonia gas

71
Q

how is ammonia gas made

A

from the reversible reaction of nitrogen from the air and hydrogen from natural gas

72
Q

equilibrium position

A

the percentages of the products and reactants at equilibrium

73
Q

what can alter the equilibrium position

A

temperature, pressure and concentration

74
Q

what can alter the equilibrium position

A

temperature, pressure and concentration

75
Q

in general equilibrium position shifts to…

A

minimise the effects of any changes to the system

76
Q

if you increase temp, where does the equilibrium position shift to

A

in the endothermic direction (transferring energy from the surroundings, cooling them down)

77
Q

if you decrease temp, where does the equilibrium position shift to

A

in the exothermic direction (transferring energy to the surroundings, heating them up)

78
Q

if you increase pressure, where does the equilibrium position shift to

A

in the direction that forms fewer gas molecules (as this reduces pressure)

79
Q

if you decrease pressure, where does the equilibrium position shift to

A

in the directions that forms more gas molecules (as this increases pressure)

80
Q

if you increase concentration, where does the equilibrium position shift to

A

in the direction that used up the substance that has been added

81
Q

if you decrease concentration, where does the equilibrium position shift to

A

in the direction that forms more of the substance that has been removed

82
Q

where are transition metals in the periodic table

A

in the central block of the periodic table

83
Q

transition metals physical properties

A
  • malleable (can be hammered or rolled into shape without shattering)
  • ductile (can be stretched out to make thin wires)
  • good conductors of electricity
  • shiny when polished
    unlike groups 1&2:
  • high melting points
  • high density’s
84
Q

how do u identify the transition metals ion present in a substance

A

the colour it of the transition metals ion present hydroxide

85
Q

why are transition metals used in catalytic converters in vehicles

A

because transition metals and their compounds typically show catalytic activity

86
Q

what happens when metals react w oxygen

A

they oxidise to form metal oxides

87
Q

what do metals form on the outside when they oxidise and why

A

they may form a thin layer of tarnish to stop oxygen reaching the metal preventing further oxidation

88
Q

what do metals form on the outside when they oxidise and why

A

they may form a thin layer of tarnish to stop oxygen reaching the metal preventing further oxidation

89
Q

what protects aluminium from further oxidation

A

it is protected by a natural layer of its oxide - this layer is thin enough to see the aluminium underneath

90
Q

When does corrosion happen?

A

Corrosion happens when a metal continues to oxidise and so the metal becomes weaker over time

91
Q

Rusting

A

Corrosion of iron or steel -> iron rust when it reacts to oxygen and water

92
Q

How can rusting be prevented?

A
  • air is kept away -> this is achieved by storing the metal in an unreactive atmosphere of nitrogen or argon
  • If water is kept away -> using a desiccant powder that absorbs water vapour
  • Coating/painting with plastic, oiling and greasing
93
Q

Sacrificial protection

A

A method of rust prevention that does not rely on keeping air of water away; instead a piece of magnesium or zinc is attached to the iron or steel object
-> magnesium and zinc oxidise more easily than iron so oxygen reacts with them rather than the iron or steel object (they lose electrons more easily) - this protection continues until the sacrificial metal corrode away

94
Q

What is a electroplating?

A

It coats the surface of one metal with a thin layer of another metal

95
Q

When is electroplating used?

A
  • To make cheap jewellery look attractive by coating it in silver or gold
    -To improve a metal objects ability to resist corrosion
96
Q

What metal resist corrosion and is used on vehicles

A

Chromium -> the thin layer of chromium stops air and water reaching the steel below preventing the object rusting

97
Q

tarnish

A

when a metal looses it colour due to chemical reaction and oxidisation

98
Q

silver and copper cables + and -

A

+ best electrical conductors
- tarnish in air

99
Q

+ and - of gold-plated connectors

A

expensive hi-if cables and electronic equipment use gold-played connectors
+ does not tarnish
- more expensive than silver or copper cables

100
Q

what do u need to electroplate a metal object

A
  • an anode made from the plating metal
  • an electrolyte which is a solution containing ions of the plating material
  • a cathode which is the metal object itself
101
Q

Electroplating

A

uses electrolysis to deposit a thin layer of one metal onto the surface of another metal

102
Q

process of electroplating, example: silver onto a copper ring

A
  • a direct flows through the electrodes and the electrolyte
  • silver ions in the electrolyte move to the negatively-charged copper ring - they gain electrons and are deposited as silver atoms
  • at the silver anode, silver atoms loose electrons or become silver ions, which go into the electrolyte
  • the longer the current flows the thicker the silver layer on the ring becomes
103
Q

what gets formed at the anode in electroplating

A

the unreactive metal looses electrons and turns from an atom to ions which go into the electrolyte move

104
Q

what is produced at the cathode in electroplating

A

The more unreactive metal ions from the anode move to the more reactive metal in the electrolyte, they gain electrons and are deposited as a unreactive metal ion

105
Q

Half equation at the anode

A

unreactive metal atom -> unreactive metal ion + e-

106
Q

half equation at cathode

A

More unreactive metal ion + e- -> more unreactive atom

107
Q

galvanising

A

iron and steel objects can be protected from rusting by coating them with zinc
-> layer of zinc improves corrosion resistance by stopping the water, reaching the iron or steel and by acting as a sacrificial metal - superficial protection can continue even if the zinc layer is damaged

108
Q

how can galvanising be carried out?

A

Using electroplating or by dipping the object in molten zinc

109
Q

alloy

A

a mixture of a metal elements with one or more other elements, usually elements

110
Q

alloys steels

A

made by deliberately adding other elements to iron

111
Q

what does stainless steel resist

A

Stainless steel resist rusting, unlike other alloy steels and iron

112
Q

what does stainless steel contain

A

contains chromium which reacts with oxygen in the air and a layer of chromium oxide forms - this is thick enough to stop air and water reaching the metal below

113
Q

How do you know whether steel is stronger or harder?

A

in general, the greater the carbon content of steel, the string and harder it is
- mild steel has a low carbon content

114
Q

Explain how are metals are malleable and ductile

A

In a solid pure metal, the atoms are all the same size and are arranged regular in layers. These layers move past each other if enough force is applied.

115
Q

Why are alloys stronger than pure metal (structure)

A

In an alloy the atoms of other elements present may be different sizes, they distort the regular structure making it more difficult for the layers of slide each - This is why alloys are stronger than pure metals.

116
Q

properties or metal alloys

A
  • chemical properties such as resistance to corrosion
  • physical properties, such as density and ability to conduct electricity
117
Q

Give a use of metals and alloys

A
  • Gold and copper could be electrical wiring
  • Aluminium could be used for overhead electrical cables
  • brass is used for making electrical plug pins
118
Q

describe how after power supply has been switched off you can measure the mass of the metal

A

rise and dry electrode and measure mass of electrode and subtract og mass

Chemistry GCSE (8 decks)

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