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Chemistry 9-1 iGCSE Oxford AQA > Chemical Changes & Metals > Flashcards

Chemical Changes & Metals Flashcards

1
Q

How reactivity determined for metals?

A

Reactivity is determined how easily they lose electrons

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2
Q

The higher up a metal is in the reactivity series means…

A

The more easily it’ll form positive ions (and the more easily it’ll react with water or acid)

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3
Q

What happens when metals react with water or an acid?

A

They lose electrons and form positive ions

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4
Q

Metals below hydrogen in the reactivity series will…

A

Not react with acid

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5
Q

Metals above hydrogen in the reactivity series will…

A

React with acids

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6
Q

How can metals that are less reactive than carbon be extracted from their ores?

A

By reduction with carbon

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7
Q

How can metals that are more reactive than carbon be extracted from their ores?

A

Using electrolysis

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8
Q

Recite the reactivity series

A

Potassium

Sodium

Lithium

Calcium

Magnesium

Carbon

Zinc

Iron

Hydrogen

Copper

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9
Q

Acid + Metal →

A

Salt + Hydrogen

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10
Q

Metal + Water →

A

Metal Hydroxide + Hydrogen

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11
Q

How will very reactive metals (potassium, sodium, lithium, calcium) react with acid?

A

They’ll react explosively

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12
Q

How will less reactive metals (magnesium, zinc, iron) react with acid?

A

Less violently (than very reactive materials)

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13
Q

Will copper react with cold, dilute acid?

A

No

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14
Q

The more reactive metal is, the ____ the reaction will go

A

faster

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15
Q

What is the speed of reaction (metal + acid) indicated by?

A

Rate of the bubbles of hydrogen given off

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16
Q

What metals will react with water?

A

Reactive metals like potassium, sodium, lithium & calcium

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17
Q

What metals will not react with water?

A

Less reactive metals like zinc, iron & copper

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18
Q

How does magnesium react with cold, dilute acid?

A

Vigorously and produces a lot of bubbles

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19
Q

How does zinc and iron react with cold, dilute acid?

A

Fairly slowly (speed up if heated)

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20
Q

How can smelting be used to obtain copper?

A

Heat copper ores in a furnace to extract high concentrations of copper

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21
Q

What is an advantage of smelting?

A

Get large amounts of copper

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22
Q

What is a disadvantage of smelting?

A

Time consuming

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23
Q

How can bioleaching be used to obtain metal?

A

Uses bacteria to produce leachate solutions that contain metal compounds

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24
Q

What is an advantage of bioleaching?

A
  1. More simpler/cheaper to operate/maintain
  2. Environmentally friendly
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25
Q

What is a disadvantage of bioleaching?

A

Very slow (compare to like smelting)

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26
Q

How can phytomining be used to obtain copper?

A
  1. Crops are planted on soil that contains very small amounts of copper
  2. The plants absorb the copper through their roots
  3. Plants are burnt to ashes to extract copper
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27
Q

What is an advantage of phytomining?

A

Easier to use plants than mining - cheaper

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28
Q

What is a disadvantage of phytomining?

A

Metal is poor quality - many impurities

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29
Q

How can electrolysis be used to obtain copper?

A

Electricity is used to break down copper compounds into copper elements

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30
Q

What is an advantage of electrolysis?

A

Get pure copper atoms

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31
Q

What is a disadvantage of electrolysis?

A
  1. Takes a lot of electricity
  2. Expensive
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32
Q

What is an alloy?

A

Mixture of at least two elements, where at least one of these is a metal

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33
Q

How are the atoms arranged in a metal?

A

There are layers of metal atoms which can move easily

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34
Q

How are the atoms arranged in an alloy?

A

Layers of atoms in alloys are disrupted so they don’t move easily

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35
Q

How are alloys made?

A

By adding another element to a metal = disrupts structure of metal, making alloys harder than pure metals

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36
Q

Acid + Metal Carbonate →

A

Salt + Water + Carbon Dioxide

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37
Q

What is thermal decomposition?

A

When heat is used to break substances down

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38
Q

Do all carbonates of metals in Group 1 decompose at temperatures reached by a Bunsen burner?

A

No

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39
Q

Why aren’t most metals found in earth in their pure forms?

A

They’re fairly reactive so they’re found as compounds

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40
Q

What is an ore?

A

A type of rock that contains metal compounds

41
Q

What are native metals?

A

Metals are so unreactive that they’re found in their elemental form (silver, gold)

42
Q

What is oxidation?

A

Gain of Oxygen

43
Q

What is reduction?

A

Loss of Oxygen

44
Q

Why can only metals below carbon in the reactivity series be extracted by reduction using carbon?

A

Because carbon can only take oxygen away from metals which are less reactive than it

45
Q

What does OIL RIG stand for?

A

Oxidation is Loss, Reduction is Gain

46
Q

What is REDOX?

A

REDuction and OXidation happen at the same time

47
Q

Write the 2 half ionic equations & the ionic equation for when chorine reacts with potassium bromide solution (halogens)

A
48
Q

Write the 2 half ionic equations & the ionic equation for when iron reacts with dilute sulfuric acid

A
49
Q

What is a displacement reaction?

A

When a more reactive metal replaces a less reactive metal from its compound

50
Q

In a displacement reaction, what happens to the metal ions?

A

Gain electrons and are reduced

51
Q

In a displacement reaction, what happens to the metal atoms?

A

Loses electrons and is oxidised

52
Q

What is are metal displacement reactions essentially?

A

Redox reactions

53
Q

What is electrolysis?

A

Passing electric current through molten/dissolved ionic substances to break them down into elements

54
Q

What is an electrolyte?

A

Molten or dissolved ionic compound (so ions are free)

55
Q

Explain the electrolysis process

A
  1. Electric current passes through electrolyte
  2. Ions move towards electrodes - where they react = compound decomposes
    1. Negative ions in electrolyte will move towards anode (+ve electrode) & lose electrons (they’re oxidised) = form uncharged element
    2. Positive ions in electrolyte will move towards cathode (-ve electrode) & gain electrons (they’re reduced) = form uncharged element
  3. This creates flow of charge through electrolyte as ions travel to electrodes
56
Q

Why can’t an ionic solid be electrolysed?

A

Ions in fixed positions - can’t move

57
Q

Why can we electrolyse molten ionic compounds?

A

Electrolysed bc ions can move freely + conduct electricity

58
Q

What type of material are electrodes made from and why?

A

From inert material = don’t react with electrolyte

59
Q

Molten ionic compounds are always…

A

broken up into their elements

60
Q

Explain how aluminium is extracted from its ore

A
  1. Aluminium is extracted from ore bauxite by electrolysis
  2. Aluminium oxide = very high melting temperature ∴ mixed with cryolite to lower melting point
  3. Molten mixture contains free ions - conduct electricity
  4. Positive Al3+ ions attracted to negative electrode, where they pick up 3 electrons & turn into neutral aluminium atoms → sink to bottom of electrolysis tank
  5. Negative O2- ions are attracted to positive electrode, where they each lose two electrons → neutral oxygen atoms then combine to form O2 molecules
61
Q

Why does the anode need to regularly replaced when extracting aluminium from its ore?

A

Made from carbon = regularly reacts with oxygen to produce carbon dioxide

62
Q

What is the ionic half equation at the negative electrode? (aluminium extraction)

A

Al3+ + 3e- → Al

63
Q

What is the ionic half equation at the positive electrode? (aluminium extraction)

A

2O2- → O2 + 4e-

64
Q

What is word equation for aluminium extraction?

A

Aluminum oxide → aluminium + oxygen

65
Q

What is symbol equation for aluminium extraction?

A

2Al2O3(l) → 4Al(l) + 3O2(g)

66
Q

Name 3 energy costs of extracting aluminium

A
  1. Bauxite purification
  2. Aluminum ore has to be minded
  3. Extracting aluminium
  4. Carbon anodes are replaced regularly
67
Q

Name 3 environmental costs of extracting aluminium

A
  1. Fuels used to keep aluminium hot
  2. Make CO2 because carbon is used for anode
  3. Electricity is used
68
Q

What is brine?

A

Solution of sodium chloride & water

69
Q

What does the electrolysis of brine produce?

A

Chorine, hydrogen and sodium hydroxide

70
Q

Name 3 uses of chlorine

A
  1. Disinfectant and purifier
  2. Manufacture of hydrochloric acid
  3. Making plastics
71
Q

Name 2 uses of hydrogen

A
  1. Manufacture of hydrochloric acid
  2. Potential as a pollution-free fuel
72
Q

Name 4 uses of sodium hydroxide

A
  1. Removing pollutants from water
  2. Processing food products
  3. Manufacture of paper
  4. Soap production
73
Q

Where is the object being electroplated made?

A

At the cathode (in an electrolysis cell)

74
Q

Where is the plating metal made (electroplating)?

A

At the anode

75
Q

When electroplating, what does the electrolyte contain?

A

Contains ions of plating metal

76
Q

When electroplating, at the anode (made of zinc), what happens?

A
  1. Zinc atoms in electrode are oxidised
  2. Lose 2 electrons each & form zinc ions
  3. Which leave anode and go into solution
77
Q

When electroplating, at the anode (made of zinc), what is the half ionic equation?

A

Zn(s) → Zn2+(aq) + 2e-

78
Q

When electroplating, at the cathode (where copper foil is to be plated), what happens?

A
  1. Zinc ions from solution are reduced
  2. Gain 2 electrons & form zinc atoms
  3. Which are deposited on copper cathode
79
Q

When electroplating, at the cathode (where copper foil is to be plated), what is the half ionic equation?

A

Zn2+ (aq) + 2e- → Zn(s)

80
Q

Why are objects electroplated? (name 3 reasons)

A
  1. To improve their appearance
  2. To protect their surface
  3. To use smaller amounts of precious material
81
Q

Electrolysis: What ions are there in aqueous solutions?

A
  1. Hydrogen ions (H+) and hydroxide ions (OH-) from water
  2. Ions from ionic compound
82
Q

Electrolysis of Aqueous Solutions: Which ions are discharged at electrodes when solution is electrolysed depends on…

A

relative reactivity of all ion in solution

83
Q

Electrolysis of Aqueous Solutions: At the cathode, if H+ ions & metal ions are present…

A

Hydrogen gas will be produced if metal ions form elemental metal that’s more reactive than hydrogen

84
Q

Electrolysis of Aqueous Solutions: At the cathode, if metal ions form element metal that’s less reactive than hydrogen…

A

Solid layer of pure metal will be produced instead which coats cathode

85
Q

Electrolysis of Aqueous Solutions: At the anode, if OH- and halide ions are present…

A

Molecules of chlorine, bromine or iodine formed

86
Q

Electrolysis of Aqueous Solutions: At the anode, if no halide ions are present…

A

OH- ions discharged and oxygen formed

87
Q

Electrolysis of Copper Sulfate Solution: Why does copper coat the cathode?

A

Because copper is less reactive than hydrogen so at the cathode it’s produced

88
Q

Electrolysis of Copper Sulfate Solution: Why are oxygen and water produced at the anode?

A

No halide ions present

89
Q

Electrolysis of Copper Sulfate Solution: What is the half ionic equation at the cathode?

A

Cu2+ + 2e- → Cu

90
Q

Electrolysis of Copper Sulfate Solution: What is the half ionic equation at the anode?

A

4OH- → O2 + 2H2O + 4e-

91
Q

Electrolysis of Sodium Chloride Solution: Why is hydrogen gas produced at the cathode?

A

Sodium metal is more reactive than hydrogen

92
Q

Electrolysis of Sodium Chloride Solution: Why is chlorine gas produced at the anode?

A

Chloride ions are present in the solution

93
Q

Electrolysis of Sodium Chloride Solution: What is the half ionic equation at the cathode?

A

2H+ + 2e- → H2

94
Q

Electrolysis of Sodium Chloride Solution: What is the half ionic equation at the anode?

A

2Cl- → Cl2 + 2e-

95
Q

What does cryolite do to aluminium oxide?

A

Lowers its melting point?

96
Q

How does cryolite lower aluminium oxide’s melting point?

A

Weakens attractions in aluminium oxide

97
Q

Explain how carbon dioxide is produced at the anode during the electrolysis of aluminium oxide (4 marks)

A
  • Oxide/O2- ions attracted to anode
  • Oxygen gas is produced
  • Anodes made from carbon
  • Carbon reacts with oxygen to produce CO2
98
Q

What does (aq) - aqueous mean?

A

Dissolved in water

99
Q

Electrolysis of Aqueous Solutions: Why do you get H+ and OH- ions?

A

Bc water molecules ionise (spilt), forming them

Chemistry 9-1 iGCSE Oxford AQA (11 decks)

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