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Chemistry (N.A.) > Unit 9.4+ [Reactivity Series, Electrolysis] > Flashcards

Unit 9.4+ [Reactivity Series, Electrolysis] Flashcards

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1
Q

Reacts vigorously with water

Most?

A

K, Na, Ca

Most K
Then Na
Then Ca

[REFER to paper!]

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2
Q

Describe the reaction:

GENERAL, GO FURTHER DOWN IN CARDS FOR TEACHER NOTES.

potassium, sodium and calcium with cold water - provides metal hydroxide + H2

  1. K (violently)
A

Potassium: Reacts violently with cold water, producing potassium hydroxide and hydrogen gas. The reaction is exothermic, often igniting the hydrogen.

w/ acid, reacts explosively

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3
Q
  1. Na (violently)
A

Sodium: Exhibits a less intense reaction than potassium but still produces sodium hydroxide and hydrogen gas. The reaction is also exothermic but less violent.

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4
Q
  1. Ca (less violently)
A

Calcium: Shows a more moderate reaction with water, forming calcium hydroxide and hydrogen gas. The reaction is less vigorous compared to potassium and sodium.

+ also w/ hot water

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5
Q

Describe the reaction: magnesium with steam -

producing metal oxide + H2

e.g. Al, Fe as well

A

Unlike alkali metals, Mg does not react noticeably with cold water.

When exposed to steam, it reacts to form magnesium oxide and hydrogen gas. This reaction is less vigorous and indicates magnesium’s lower reactivity compared to alkali metals.

Magnesium reacts with steam to form magnesium oxide and hydrogen.

Mg (s) + H2O (g) -> MgO + H2

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6
Q

no reaction w/ water whether hot (l), cold (l) or steam (g)

A

lead, copper, silver, gold

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7
Q

describe reaction: magnesium, zinc, iron, copper, silver and gold

with dilute hydrochloric acid

  1. Mg
A

Mg → Reacts rapidly/vigorously with dilute hydrochloric acid, producing magnesium chloride and hydrogen gas. Reaction is vigorous.

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8
Q
  1. Zinc
A

Zn → Also reacts with dilute hydrochloric acid but at a slower rate than magnesium, producing zinc chloride and hydrogen gas.

reacts slowly

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9
Q
  1. Iron
A

Fe → Shows a slower reaction compared to zinc, forming iron(II) chloride and hydrogen gas.

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10
Q
  1. Copper
A

Cu → Barely reacts with dilute hydrochloric acid, indicating its low reactivity.

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11
Q
  1. Silver & Gold
A

Ag & Au → Do not react with dilute hydrochloric acid. Their position in the reactivity series explains their lack of reactivity.

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12
Q

Why does this trend exist?

A

Ag & Au cannot displace hydrogen from HCl. Silver is below hydrogen in the reactivity series and thus cannot displace it.

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13
Q

Metals that react vigorously, producing a lot of heat and gas quickly, like potassium and sodium, are considered…

A

highly reactive

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14
Q

Metals that react slowly or not at all, like silver and gold, are considered…

A

less reactive

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15
Q

Describe relative reactivities of metals w/ tendency to form positive ions, by
displacement reactions, if any, with the aqueous
ions of Mg, Zn, Fe, Cu, & Ag

Bc

How easily do highly reactive metals lose electrons?

A

Reactivity is closely linked to a metal’s tendency to form positive ions:

Highly reactive metals like potassium and sodium lose electrons easily, forming positive ions rapidly.

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16
Q

How easily do less reactive metals lose electrons?

A

Less reactive metals like silver and gold have a lower tendency to lose electrons and form positive ions.

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17
Q

Aluminium, though high in the reactivity series, often appears less reactive

Why?

A

due to the formation of a protective oxide layer on its surface, which prevents further reaction with air or water.

Once this layer is removed or disrupted, aluminium’s true reactivity is observed.

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18
Q

Why is potassium more reactive?

A

Though K and Na both have 1 valence electron,

K’s valence electron is further from the nucleus so it is easier to lose that electron to become a cation.

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19
Q

Why is potassium more reactive than calcium specifically?

Consider electronic configuration

A

Both have four electron shells

BUT the more protons in the nucleus, the harder it is to lose a valence electron to become a cation

+ 1 valence electron is easier to lose than 2

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20
Q

Metal, Reaction with water

  1. Calcium
A

Bubbles of gas are given off after a few seconds.

When tested with universal indicator the water is now alkaline

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21
Q
  1. Sodium
A

The sodium melts and skims over the surface producing a stream of small bubbles.

Sometimes a yellow-orange flame appears

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22
Q

Potassium

A

It immediately produces a lilac flame as it skims around the surface making a fizzing noise

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23
Q

What does this stand for:

Please send Charlie’s monkeys and carbon zebras in tall lead hellish cages securely guarded.

A

POTASSIUM
SODIUM
CALCIUM
MAGNESIUM
ALUMINIUM
Carbon
ZINC
IRON
Tin
LEAD
Hydrogen
COPPER
SILVER
GOLD

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24
Q

Practical Implications

A

Predicting Reactions: It helps in predicting the outcome of reactions involving different metals.

Extraction of Metals: The method of metal extraction from its ore is often determined by its position in the series.

Corrosion and Protection: Understanding reactivity helps in developing methods to protect metals from corrosion.

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25
Q

In a displacement reaction…

A

the metal in a compound is replaced by the more reactive metal to form a new compound

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26
Q

Mg + CuSO4 =>

A

Cu + MgSO4

bc Mg more reactive so Cu replaced

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27
Q

Define electrolysis

A

the decomposition of an
ionic compound, when molten or in aqueous solution, by the passage of an electric current

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28
Q

anode

A

positive electrode

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29
Q

cathode

A

negative electrode

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30
Q

electrolyte

A

the molten or aqueous
substance that undergoes electrolysis

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31
Q

Describe the transfer of charge during electrolysis to include:

(a) the movement of electrons in the external circuit

(b) the loss or gain of electrons at the electrodes

(c) the movement of ions in the electrolyte

A

a)

b)

c)

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32
Q

State where metals/hydrogen are formed?

Where are non-metals (except hydrogen) formed?

A

metals or hydrogen are formed at the cathode and that non-metals (other than
hydrogen) are formed at the anode

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33
Q

Why are metal objects electroplated?

A

metal objects are electroplated to improve their appearance and resistance to
corrosion

34
Q

How does a hydrogen-oxygen fuel cell work?

A

hydrogen–oxygen fuel cell uses
hydrogen and oxygen to produce electricity with
water as the only chemical product

35
Q

Extraction of Metals

What are ores?

A

Some unreactive metals can be found as elements. Native metals.

Most metals found naturally in rocks - called ores. In compounds, chemically bonded to other elements.

36
Q

Metals below carbon are…

A

Extracted by REDUCTION

using carbon, coke, or charcoal

cheap process as carbon is cheap & can be source of heat

37
Q

Unreactive metals do not…

A

They do not need to be extracted - found as pure element (native)

occurs as they do not easily react with other substances due to their chemical stability

38
Q

Metals above carbon

Why?

A

Extracted by electrolysis

Bc the REACTIVITY of a metal determines the METHOD of extraction

large amount of electricity required so expensive

39
Q

Aluminium extraction using?

What is bauxite?

Properties

A

Electricity, by electrolysis of molten bauxite

Most common aluminium ore Al2O3

Bauxite - high melting point 2000 Celsius.

40
Q

Why is aluminium oxide dissolved in molten cryolite?

REMEMBER the word “cryolite”

A

reduce the overall melting point of the mixture, making it easier to melt and reducing electricity required for electrolysis process

cryolite used as: -lowers operating temperature
-increases conductivity

41
Q

Overall

A

4Al2O3 (l) -> 4Al (l) + 3O2 (g)

42
Q

Ionic main equation

A

2Al2O3 -> 4Al3+ + 6O2-

43
Q

Half equations

At the NEGATIVE cathode

A

Al3+ + 3e- -> Al

44
Q

At the positive anode

A

2O2- -> O2 + 4e-

45
Q

On diagram, there is

A

Graphite anode [in middle, positive)

Graphite cathode [bracketing anode, negative]

Molten aluminium coming out right

Purified aluminium ore dissolved in molten cryolite

+ Steel case

46
Q

The Process of Aluminium Extraction by Electrolysis

1.

A

Bauxite is first purified to produce aluminium oxide, Al2O3

47
Q

2.

A

Aluminium oxide is then dissolved in molten cryolite

This is because aluminium oxide has a melting point of over 2000°C which would use a lot of energy and be very expensive

The resulting mixture has a lower melting point without interfering with the reaction

48
Q

3.

A

The mixture is placed in an electrolysis cell, made from steel, lined with graphite

49
Q
  1. What does graphite lining do?
A

The graphite lining acts as the negative electrode, with several large graphite blocks as the positive electrodes

50
Q

At the cathode (negative electrode):

REDUCTION = GAIN E-

FORM AL

A

Aluminium ions gain electrons (reduction)

Molten aluminium forms at the bottom of the cell

The molten aluminium is siphoned off from time to time and fresh aluminium oxide is added to the cell

Al3+ + 3e- → Al

51
Q

At the anode (positive electrode):

A

Oxide ions lose electrons (oxidation)

Oxygen is produced at the anode:

2O2- → O2 + 4e-

52
Q

The overall equation for the reaction is:
2Al2O3 → 4Al + 3O2

The carbon in the graphite anodes reacts with the oxygen produced to produce CO2
C (s) + O2 (g) → CO2 (g)

As a result the anode wears away and has to be replaced regularly

A lot of electricity is required for this process of extraction, this is a major expense

A
53
Q

Why aluminium used for foil & food cans

A

Doesn’t corrode easily bc has a strong oxide coating on its surface, which protects the aluminium from further reaction

54
Q

Why in aerospace industry?

A

Has low density, light

55
Q

Extraction of Iron from Hematite

Where? From its…?

This produces how many tonnes of iron/day?

A

Iron is extracted in a large container called a blast furnace from its ore, hematite

Modern blast furnaces produce approximately 10,000 tonnes of iron per day

56
Q

Raw materials

added where?

A

iron ore (hematite)

coke (an impure form of carbon)

& limestone

are added into the top of the blast furnace

57
Q

What is blown into the bottom?

A

Hot air

58
Q

Zone 1

A

Carbon-rich coke burns in the hot air blasted in to the furnace, reacting with oxygen in air, to produce carbon dioxide.

The reaction = exothermic so it gives off heat, heating the furnace. Produces lots of heat energy

C (s) + O2 (g) -> CO2 (g)
carbon + oxygen → carbon dioxide

59
Q

Zone 2

A

The carbon dioxide reacts with more hot coke to form carbon monoxide [at high temp in furnace]

Carbon dioxide has been reduced to carbon monoxide

CO2 (g) + C (s) -> 2CO (g)
carbon + carbon dioxide → carbon monoxide

60
Q

Zone 3

A

The carbon monoxide then reacts w/ the iron oxide from the haematite to produce CO2 and Fe; it reduces the iron oxide [in the iron ore] to form iron

This will melt and collect at the bottom of the furnace, where it is tapped off:

Fe2O3 (s) + 3CO (g) -> 2Fe (l) + 3CO2 (g)

iron(III) oxide + carbon monoxide → iron + carbon dioxide

61
Q

Why is limestone, CaCO3, added?

A

added to the furnace to remove impurities in the ore.

62
Q

Limestone thermally decomposes to form CaO and the product further reacts with the impurities to form slag, CaSiO3.

The calcium oxide formed reacts with the silicon dioxide, which is an impurity in the iron ore, to form calcium silicate

What happens to it then?
Equations?

A

CaCO3 (s) -> CaO (s) + CO2 (g)
calcium carbonate → calcium oxide + carbon dioxide

CaO (s) + SiO2 (s) -> CaSiO3 (s)
calcium oxide + silicon dioxide → calcium silicate

melts and collects as a molten slag floating on top of the molten iron, which is tapped off separately

63
Q

Actual equation cards - test self: symbol equations for the different stages of the extraction of iron from hematite are:

  1. Zone 1: The burning of carbon (coke) to provide heat and produce carbon dioxide:
A

C (s) + O2 (g) → CO2 (g)

64
Q

Zone 2: The reduction of carbon dioxide to carbon monoxide:

A

CO2 (g) + C (s) → 2CO (g)

65
Q

Zone 3: The reduction of iron(III) oxide by carbon monoxide:

A

Fe2O3 (s) + 3CO (g) → 2Fe (I) + 3CO2 (g)

66
Q

The thermal decomposition of calcium carbonate (limestone) to produce calcium oxide:

A

CaCO3 (s) → CaO (s) + CO2 (g)

67
Q

The formation of slag:

A

CaO (s) + SiO2 (s) → CaSiO3 (l)

Acid-base reaction

68
Q

Name the three products formed when tin(II) nitrate is heated.

oxidised, NO2, O2

A

tin oxide, nitrogen dioxide, oxygen

69
Q

Steel articles can be plated with tin or zinc to prevent rusting.

When the zinc layer is damaged exposing the underlying steel, it does not rust, but when
the tin layer is broken the steel rusts.

Explain. [4]

A

zinc is more reactive than iron [1]

tin is less reactive than iron [1]

zinc provides sacrificial protection [1]

Iron corrodes/reacts [1]

70
Q

Explain why it is necessary to use a mixture, alumina and cryolite, rather than just
alumina.

A

lowers melting point [1]

reduces amount of energy needed / reduces cost

71
Q

Explain, in terms of electron transfer, why the more reactive metal is always the negative
electrode.

A

metals react by losing electrons (1)

the more reactive metal/ zinc will lose electrons more readily (making the
electrode negatively charged). (1)

72
Q

dissolving → filtration → evaporation → crystallisation

🔗

Four steps to prepare a salt from an excess of a solid base and an acid:

neutralisation -> evaporation -> filtration -> crystallisation

//

2, 1, 2, 3

filter, concentrate resulting solution, filter, heat crystals

A
73
Q

Salts can be made by adding different substances to dilute hydrochloric acid.

For which substance could any excess not be removed by filtration?

A

C) sodium hydroxide

The substance for which any excess cannot be removed by filtration is sodium hydroxide (C). When sodium hydroxide is added to dilute hydrochloric acid, a neutralization reaction occurs, resulting in the formation of water and a salt called sodium chloride.

74
Q

Which method is used to make the salt copper sulfate?

A

dilute acid + carbonate

75
Q

Which of the following methods are suitable for preparing both zinc sulfate and copper sulfate?

1
2
3
Reacting the metal oxide with warm dilute aqueous sulfuric acid.
Reacting the metal with dilute aqueous sulfuric acid.
Reacting the metal carbonate with dilute aqueous sulfuric acid.

A

B) 1 and 3 only

76
Q

A compound is a salt if it

A

is formed when an acid reacts with a base.

77
Q

Salts can be prepared by reacting a dilute acid

1 with a metal;
2 with a base;
3 with a carbonate.

Which methods could be used to prepare copper(II) chloride?

A

2 & 3 only

78
Q

Which methods of salt preparation are suitable for copper(II) chloride?

1 Add copper(II) carbonate to dilute hydrochloric acid.
2 Add copper to dilute hydrochloric acid.
3 Warm copper(II) oxide with dilute hydrochloric acid.

A

1 & 3

Copper does not react with acid because in the reactivity series copper is placed below the hydrogen.

The reaction between copper(II) carbonate and dilute hydrochloric acid is shown below.

CuCO3+2HCl⟶CuCl2 + H2O+CO2

The reaction between copper (II) oxide and dilute hydrochloric acid is shown below.

CuO+2HCl→CuCl2 +H2O

79
Q

BELOW HYDROGEN means

A

DOES NOT REACT W/ ACID

80
Q

Describe the stages in the preparation of a sample of DRY copper sulfate crystals using SULFURIC ACID and COPPER(II) OXIDE and the following equipment. Include a balanced equation. (7 marks)

A

React EXCESS copper oxide with sulfuric acid

Stir and heat mixture in a conical flask

Filter off excess black solid (copper oxide)

Concentrate solution by heating in an evaporating basin

Leave to stand and cool slowly to form crystals

Dry crystals between filter papers/in oven

CuO(s) + H2SO4(aq) → CuSO4(aq) + H2O (l)

Chemistry (N.A.) (10 decks)

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