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Chemistry Gcse > ⭐️SC10, SC11, SC12, SC13-electrolysis, transition metals, reversible reactions > Flashcards

⭐️SC10, SC11, SC12, SC13-electrolysis, transition metals, reversible reactions Flashcards

1
Q

What is an electrolyte?

A

An ionic substance with freely moving ions and so can conduct electricity

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2
Q

What is electrolysis?

A

Using energy transferred by electricity to decompose electrolytes

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3
Q

What are the two types of ions and what electrode do they move to?

A

-cations are positively charged and move to the negative cathode
Anions are negatively charged and move to fee positive anode

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4
Q

How can you prove positive ions go to negative cathode and vise versa?

A

By placing purple potassium magnganate crystal on a piece of damp filter paper attached to a microscope slide and connected to a DC electric supply, the purple colour will spread towards the anode

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5
Q

What happens to ions in terms of the electrons at each cathode and what is each process called?

A

At the anode, negative ions loose electrons which is oxidation
At the cathode electrons are transferred from electrode to positive ion so it gains electrons

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6
Q

What does oxidation and reduction do to the ions at the electrodes?

A

It changes charged ions into atoms or molecules resulting in chemical changes at the electrodes

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7
Q

What type of electrolysis uses inert (unreactive) electrodes?

A

Electrolysis of molten or dissolved ionic salts

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8
Q

What material electrodes are used when electrolysing molten lead bromine?

A

Usually platinum or graphite electrodes because molten lead bromine is a dissolved ionic salt and needs electrodes to be inert

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9
Q

How is copper purified through electrolysis?

A
  • the copper needing to be purified is used at the anode and the pure one is used at the cathode, in an electrolyte of copper sulphate solution
  • copper is one dissolve in the solution and go to the cathode so anode looses mass and the cathode gains mass.
  • Impurities from the anode collect under it as a sludge
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10
Q

Why may anode sludge after electrolysis of copper sulphate solution be collected?

A

Because it could contain valuable metallic elements

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11
Q

What are the half equations at each electrode in the electrolysis of copper sulphate solution?

A

Anode:
Cu -> Cu2+ - 2e-

Cathode:
Cu2+ + 2e- -> Cu

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12
Q

In electrolysis of salt solution? How do you know if the positive ions or hydrogen ions become atoms at the cathode?

A

The more reactive ion stays in the solution

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13
Q

At the anode, how do you determine wether a hydroxide ion of the negative salt ion forms?

A

The salt forms if it’s a halogen so either f+ or cl- otherwise the OH- forms (get their checked)

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14
Q

What do the metals that react with cold water form?

A

Metal hydroxide and hydrogen

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15
Q

What do the metals that react with steam form?

A

Hydrogen and a solid metal oxide

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16
Q

What happens if a metal reacts with dilute acids? What can this tell you about the metal?

A

It forms hydrogen and a salt solution and bubbles of gas will be seen. The more bubbles the more reactive the metal

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17
Q

What does it mean if a metal is higher in the reactivity series in terms of electrons

A

The higher the metal in the reactivity series, the more easier it looses electrons

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18
Q

How do displacement reactions work?

A

The more reactive metal displaces the less reactive metal in the salt e.g.

Zn + CuSO4 -> Cu + ZnSO4

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19
Q

What are displacement reactions also known as?

A

Redox reactions

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20
Q

How do you write ionic equations?

A
  1. Write out the full balanced symbol equation with state symbols
  2. Split the aqueous ionic compounds into the ions they contain
  3. Cancel the spectator ions
  4. Write the equation that’s left
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21
Q

What is extraction?

A

The process of obtaining a metal from it’s naturally occurring compound

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22
Q

What is an ore.

A

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

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23
Q

How is iron extracted from its ore and what’s this ore called

A

Haematite is the ore iron is extracted from by heating the iron oxide with carbon as carbon is more reactive than iron and displaces it

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24
Q

How do you extract metals from their ores if they are more reactive than carbon? Give an example

A

With electrolysis for example aluminium comes from the ore bauxite and is extracted by the electrolysis of aluminium oxide

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25
Q

Why is electrolysis not used in large scale extraction of zinc

A

As zinc is less reactive than carbon so can be extracted using a displacement reaction and keeping metal oxides molten for electrolysis requires a lot of energy making it extremely expensive

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26
Q

What is bioleaching? Describe the steps involved of bioleaching to obtain copper

A

A method of metal extraction

  1. Bacteria is grown on a low grade ore producing a solution containing the copper ions called the leachate
  2. The copped is ectracted from the leachate by a displacement reaction using scrap iron
  3. The copper is then purified using electrolysis
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27
Q

What is phytoextraction?

A

Where you grow plants that absorb metal compounds and then burn them to form ash from which the metal is extracted

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28
Q

Give advantages and disadvantages of bioleaching

A

Adv:
-doesn’t require high temps
-no harmful gases produced
-causes less damage to the landscape than mining
-conserves supplies of higher grade ores
Disadv:
-very slow
-toxic substances like sulphuric acid can be produced and damage the environment

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29
Q

Give advantages and disadvantages of phytoextraction

A

Adv:
-no harmful gases produced
-causes less damage to the landscape than mining
-conserves supplies of higher grade ores
-can extract metals from contaminated soils
Disadv:
-very slow
-more expensive than mining some ores
-growing plants is dependant on weather conditions

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30
Q

What’s oxidation and reduction in terms of oxygen?

A

Oxidation is the gain of oxygen

Reduction is the loss of oxygen from a substance

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31
Q

What are redox reactions?

A

Reactions where oxidation and reduction occur?

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32
Q

When oxidation occurs…

A

Reduction occurs at the same time and so when one substance is oxidised, the other is reduced

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33
Q

What happens in the electrolysis of aluminium oxide to get aluminium?

A

The Al3+ ions are attracted to the cathode where they gain electrons to become Al and the O2- ions are attracted to the anode where they loose electrons to become O2.

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34
Q

What are the half equations for electrolysis of aluminium oxide to get aluminium?

A

Cathode: Al3+ + 3e -> Al
Anode: 2O2- -> O2 + 4e

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35
Q

What is the electrolyte when obtaining aluminium using electrolysis?

A

Aluminium oxide mixed with cryolite as this lowers the high melting point of 2000°C. The lower melting point reduced the amount of energy needed and saves money

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36
Q

In electrolysis of aluminium oxide, why must the anode be regularly replaced?

A

As At high temps, the oxygen reacts with the graphite anode to form carbon dioxide as graphite is made of carbon hydrogen

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37
Q

What is corrosion?

A

When a metal reacts with oxygen making the metal weaker over time

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38
Q

What process happens in corrosion?

A

Oxidation as the metal gains oxygen

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39
Q

What is rusting? What does it require?

A

The corrosion of iron that requires water as well as oxygen

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40
Q

Why do some fairly reactive metals not corrode quickly?

A

As they tarnish where their surfaces form a protective oxide layer that prevents further reaction

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41
Q

Give 3 advantages of recycling

A
  • natural reserves of metal ores will last linger
  • less waste metal ends up in landfill sites
  • the need to mine ores is reduced which is good as mining damages the landscape and creates noise and dust pollution
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42
Q

Give disadvantages of recycling

A

It can take a lot of energy and ninety to transport, collect and sort the metals to be recycled

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43
Q

What does a lifecycle assessment do?

A
  • works out the environmental impact of the product
  • decides wether it’s worth manufacturing a product
  • compares the effects of using different materials for the same product
44
Q

What are the stages in a lifecycle assessment?

A
  1. Obtaining and processing raw materials
  2. Manufacturing and packaging the product
  3. Using the product
  4. Disposal of the product
45
Q

Give 3 questions you would ask for a lifecycle assessment

A
  • what raw materials are needed?
  • what will the product be used for?
  • how much energy is needed for the manufacture and packaging of the product?
46
Q

What are reversible reactions?

A

Where the products react to reform the reactants

47
Q

What’s significant about the energy transferred in a reversible reaction?

A

The same amount of energy is transferred in both the forward and backward direction

48
Q

What is exothermic reaction

A

One that gives out heat and heats up the surroundings giving a negative energy change in the reaction

49
Q

What is an endothermic reaction?

A

One that takes in heat and cools it’s surroundings giving a positive energy change in the reaction

50
Q

What is dynamic equilibrium?

A

Where the % of the products are no longer changing despite the forward and backward reactions are still happening and the substances remain in balance.

51
Q

When does dynamic equilibrium occur?

A

In a closed system where there is no loss of reactants or products as in an open system, gases could escape so equilibrium wouldn’t be achieved

52
Q

What process is the manufacture of ammonia by? What does it involve? What changes the equilibrium position?

A

The Haber process.
Involves a reversible reaction between nitrogen (from air) and hydrogen (from natural gas) that can reach a dynamic equilibrium
The equilibrium position is changed by the reaction conditions?

53
Q

What are the reaction conditions did in the have process and what are they?

A

They are to favour the forward reaction and make a large amount of product as cheaply as possible.
Conditions = temp of 450°C, pressure of 200 atmospheres and an iron catalyst

54
Q

What happens to equilibrium position if you increase the temperature?

A

It shifts in the endothermic direction

55
Q

What happens to equilibrium position if you decrease temperature?

A

It shifts to the exothermic direction

56
Q

What happens to equilibrium position if you increase pressure?

A

Shifts to the direction that forms fewer gas molecules

57
Q

What happens to equilibrium position if you decrease pressure?

A

Shifts to the direction that forms more gas molecules

58
Q

What happens to equilibrium position if you increase the concentration?

A

Shifts in the direction that uses up the substance that’s been added

59
Q

What happens to equilibrium position if you decrease concentration?

A

Shifts in the direction that forms more of the substance that’s been added

60
Q

What are the physical properties of transition metals?

A
  • malleable= they can be hammered or rolled into shape without shattering
  • ductile= can be stretched out to make thin wires
  • shiny when polished
61
Q

What’s iron used for and why?

A

To make buildings, bridges, ships and cars as it’s malleable and strong

62
Q

What’s copper used for and why?

A

Electrical wiring because it’s ductile and is a good conductor of electricity

63
Q

What do household mirrors contain?

A

A sheet of glass coated with aluminium

64
Q

What metal is used in infared telescopes? Why isn’t this aluminium

A

Silver as it’s shinier than aluminium so that’s used for the mirrors in the telescopes instead

65
Q

Compared to other metals, transition metals typically have…

A

High melting points

High densities

66
Q

What are the chemical properties of transition metals?

A
  • form coloured compounds

- can be used as a catalyst

67
Q

Give an example of transition metals that show they form coloured compounds

A

Iron oxide is red brown
Tungsten oxide is yellow
Iron (II) hydroxide is pale green

68
Q

What does the rate of metals oxidising depend on?

A

Their reactivity as the more reactive they are the quicker they oxidise

69
Q

What’s a tarnish? Give an example of a metal that forms this

A

A layer formed on metals when they oxidise that stops oxygen reaching the metal itself preventing further oxidation for example the aluminium oxide on aluminium

70
Q

When does corrosion happen?

A

When a metal continues to oxidise making the metal weaker

71
Q

What is rusting?

A

The corrosion of iron or steel (mainly iron)

72
Q

When does iron rust?

A

It rusts when it reacts with oxygen and water

73
Q

What is the substance seen on rusty objects, what usually happens to it?

A

It’s hydrated iron oxide (III) and this flakes off exposing the metal to more more air air and water and so it continues to corrode and weaken

74
Q

How can you prevent rusting by keeping away the air?

A

Storing the metal in an unreactive atmosphere of nitrogen or argon

75
Q

How can you prevent rusting by keeping away both air and water at the same time

A

Painting, coating with plastic, oiling and greasing

76
Q

How can you prevent rusting by keeping away water?

A

using a desiccant powder that absorbs water vapour

77
Q

What is sacrificial protection

A

A method of rust prevention that does not rely in keeping away air or water but instead attaches magnesium or zinc to the iron or steel because they oxidise easier than iron and so oxygen reacts with them instead.

78
Q

How long does sacrificial protection last for?

A

It continues until the sacrificial metal corrodes away

79
Q

What does a metals reactivity mean in terms of loss of electrons?

A

The more reactive the metal is the more easily it loses electrons.

80
Q

Why does magnesium and zinc oxidise in preference to iron or steel? (In terms of electrons)

A

As they are more reactive and so lose electrons easier

81
Q

What is electroplating?

A

Coating the surface of one metal with a thin layer of another metal

82
Q

Why may electroplating be done?

A
  • because the metal is expensive so it’s cheaper to electroplate a cheaper metal
  • to improve a metals ability to resist corrosion
83
Q

Give an example where electroplating has been done because a metal is expensive?

A

Making jewellery by electroplating cheap base metals like iron and nickel with gold or silver so the jewellery is still attractive

84
Q

Give an example where electroplating has been done to improve a metals resistance to corrosion

A

Chromium is used to electroplate objects such as vehicle parts or boat parts made from steel making them chrome plated as the thin layer of chromium stops air and water reaching the steel below preventing the object from rusting

85
Q

How may cables and equipment use electroplating?

A

As they are usually made of copper or silver as the best electrical conductors but a layer of tarnish can form so they may be electroplated with gold despite its expensive

86
Q

What do you need to electroplate a metal object?

A
  • an anode made of the playing metal
  • an electrolyte that contains the ions of the plating metal
  • a cathode which is the metal object itself
87
Q

Give the half equations at each electrode when copper is electroplated with silver

A
  • anode: Ag -> Ag+ + e-

- cathode: Ag+ + e- -> Ag

88
Q

What is galvanising?

A

Where iron and steel objects are protected from rusting by coating them with zinc

89
Q

Why does galvanising work?

A

Because the thin layer of zinc improves corrosion resistance by stopping reaching the iron or steel and by acting as a sacrificial metal which can continue even if the zinc is damaged

90
Q

How can galvanising be carried out?

A

By using electroplating or dipping the metal into molten zinc

91
Q

Steel cans are protected on the inside by electroplating with tin. If the tin is damaged what happens to the steel can?

A

The steel will rust further because iron is more reactive than tin so it is what acts as a sacrificial metal to protect the tin

92
Q

What is an alloy?

A

A mixture of a metal element with one or more other elements that are usually metals

93
Q

What are stainless steel an alloy of? What is their benefits over iron and other steels?

A

They resist rusting as they contain chromium which reacts with the oxygen in the air forming chromium oxide which is thick enough to stop air and water reaching the metal below yet is thin enough to be transparent. If the metal scratches, more chromium reacts to replace the layer

94
Q

What makes up ‘tool steels’?

A

Tungsten and molybdenum in drill bits because they are very strong

95
Q

How do you make steel harder?

A

Increase the carbon content, the greater this is, the harder and stronger it will be

96
Q

Why doesn’t mild steel have a lot of carbon so it’s as strong as possible?

A

Because it’s purposes still require it to malleable so it has less carbon but contains manganese to increase its strength while maintaining its malleability

97
Q

What’s mild steel used for?

A

A building material and car body panels

98
Q

What do car manufacturers use stronger steel for?

A

To produce strong but relatively lightweight car bodies

99
Q

Why are metals malleable and ductile?

A

Because the atoms are all the same size and are regularly arranged when solid so layers can slide past each other if enough force is applied.

100
Q

Explain in terms of atoms why alloys are stronger than pure metals

A

As in alloys the atoms of other elements present may be different sizes, distorting the regular structure making it harder for the layers to slide past each other though this doesn’t present the alloys being ductile and malleable

101
Q

What does the uses of a metal or alloy depend on?

A
  • chemical properties like resistance to corrosion

- physical properties like density and ability to conduct electricity

102
Q

Despite both copper and gold are very good at electrical wiring why is copper used?

A

Because gold is thousands of times more expensive than copper so good is only used in tiny amounts to connect microprocessors and memory chips

103
Q

Why is aluminium used in overhead cables instead of copper despite it being less good at conducting electricity?

A

As it resists corrosion, is stronger and cheaper than copper also

104
Q

Give an example where alloys have more useful properties than the metals they contain?

A

Brass for e.g. is made of copper and zinc. Both copper and brass resist corrosion. Copper is a better electrical conductor but brass is stronger making it more suitable than copper for electrical plug pins

105
Q

What is magnalium made up of? What’s it used for?

A

95% aluminium and 5% magnesium used for aircraft parts and scientific instruments

106
Q

Why is aluminium and magnesium used together as the alloy magnalium instead of the metals alone?

A
  • magnalium is less dense and almost 4x stronger than aluminium
  • magnalium is twice as strong and has better resistance to corrosion than magnesium

Chemistry Gcse (24 decks)

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