Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry Paper 1 > Topic 5 - Electrolysis And Obtaining Metals > Flashcards

Topic 5 - Electrolysis And Obtaining Metals Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

What is electrolysis?

A

An electrical current transfers energy which allows it to decompose electrolytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is an electrolyte?

A

An ionic substance with freely moving ions

Can conduct electricity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What takes place at the cathode?

A

ReduCtion

Electrons on left of half equation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What happens at anode?

A

OxidAtion

Electrons on right of half equation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the Core Practical Electrolysis of copper sulfate solution?

A

Label one piece of copper foil the anode and the other the cathode
Set up an electrolysis circuit (put electrodes in copper sulfate solution)
Turn on power (alter resistor) so you have a current of 0.2 A
Record the current and leave for about 20mins
Turn off the power and remove electrodes from beaker
Wash electrodes with distilled water
Measure and record the mass of the electrodes and repeat experiment with different voltages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What happens when a molten salt is electrolysed?

A

Ions are discharged as atoms/molecules at the electrodes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How can you predict the electrolysis products of any molten salt?

A

The metal is produced at cathode and the non metal at anode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What else are attracted at the anode/cathode when it’s a salt solution?

A

Due to there being water, H ions are also attracted to Cathode and OH ions are attracted to anode.
However, copper ions e.t.c at the cathode are discharged more than hydrogen ions so copper is formed
Chloride ions at the anode are discharged more than the hydroxide ions so chlorine is formed as a gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why will the H ions or OH ions sometimes be produced?

A

They will discharge more easily if the metal/non metal is more reactive than hydrogen or hydroxide

E.g. h is discharged easier because na is more reactive
But cu is discharged because it’s not more reactive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where can some excess mass be found?

A

Any impurities from anode e,t,c do not form ions and collect below the anode as sludge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What elements react with water/dilute acid a lot?

A

Potassium, sodium and calcium
They form hydrogen and a metal hydroxide with water
They react violently with dilute acids
except calcium which forms hydrogen and a salt solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What elements react slowly with water/dilute acid?

A

Magnesium, aluminium, zinc, and iron
They react slowly with water by react with steam to form a hydrogen and a metal oxide
They form hydrogen and a salt solution when reacted with a dilute acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What elements do not react with water or dilute acid?

A

Copper, silver and gold

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

In all of these reactions, what happens to the metal atoms?

A

They lose electrons to form positive ions (cations)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a displacement reaction?

A

When an element will react with an element below it in the reactivity series
I.e. zinc reacts with copper and displaces it but copper can’t displace zinc because it’s not as reactive as zinc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is extraction?

A

Obtaining a metal from compounds (when reactive metals have reacted with other elements to form compounds in rock)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is an ore?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How can they be extracted?

A

You obtain the element by heating the element oxide (I,e. You get iron by heating iron oxide) with carbon as carbon is more reactive and it will displace it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do you extract ores, more reactive than carbon?

A

Electrolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How is this done?

A

Pass electricity through a molten ionic compound to decompose it into its elements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Why is electrolysis for extraction not the preferred way?

A

It’s really expensive to keep metal oxides molten for electrolysis as it requires loads of energy
So it’s only used of the element is more reactive than carbon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are some examples of elements that have to be extracted through electrolysis?

A

Potassium, sodium, calcium, magnesium and aluminium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are some examples of elements that can be extracted by heating carbon?

A

Zinc, iron and copper

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How can silver / gold be extracted?

A

Don’t need to be as they’re found as an uncombined element

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is bioleaching?

A

Uses bacteria that has grown on a low grade ore
Bacteria produce a leachate (copper ions).
The copper is extracted from the leachate by displacing it using iron, then purified by electrolysis
Also be used for metals like zinc, nickel e.t.c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is phytoextraction?

A

Growing plants that absorb metal compounds

When the plants absorb the compound, they are burnt to form ash, and the metal is extracted from ash

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are some advantages of bioleaching and phytoextraction?

A

Both: No harmful gases (e.g. sulfur dioxide) are produced
Causes less damage to landscape than mining
Conserved supplies of higher grade ores

Bio: Doesn’t require high temperatures

Phyto: can extract metals from contaminated soils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What are some disadvantages?

A

Both: very slow

Bio: toxic substances and sulfuric acid can be produced by the process and damage the environment

Phytoextraction: more expensive that mining some ores
Growing plants is dependant on weather conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is a redox reaction?

A

Reactions in which oxidation and reduction occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How is aluminium obtained by removing the oxygen from aluminium oxide by electrolysis?

A

Aluminium ions are attracted to cathode where they gain electrons to form aluminium
The oxide ions are attracted to anode where they lose electrons to form oxygen
At high temperatures, the oxygen reacts with the graphite (carbon) anodes to form carbon dioxide.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How does corrosion occur?

A

When a metal reacts with oxygen, making the metal weaker over time
The metal gains oxygen so it is oxidised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Why is rusting?

A

When iron reacts with water and oxygen over time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Why do some metals corrode faster?

A

The more reactive it is, the more rapidly it corrodes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Why is gold used in jewellery?

A

It doesn’t corrode at all

35
Q

How can some metals prevent themselves from corroding?

A

Metals like aluminium produce a protective oxide layer (tarnish) on its surface

36
Q

What are some advantages of recycling?

A

Natural reserves of metal ores will last longer
Reduce need to mine ores (mining can damage landscape and create pollution and noise)
Less pollution produced because gases like sulfur dioxide are produced when metals are extracted from metal sulfide ores
Less energy to recycle than extracting
Less waste ends up in landfill

37
Q

What are some disadvantages?

A

Sometimes it can cost more to collect, transport and sort the metals
Take mor energy transporting

38
Q

What does the Life Cycle assessment do?

A

Helps people decide if it is worthwhile to manufacture or recycle a product

39
Q

What is a reversible reaction?

A

When products react to reform the reactants

Both the forward and backward reaction occur at same time

40
Q

What is dynamic equilibrium?

A

The reaction rate of the forward reaction is equal to the reaction rate of the backwards reaction (reversible reaction)

41
Q

What system can dynamic equilibrium occur in?

A

A closed system - otherwise gas would escape and equilibrium wouldn’t be achieved

42
Q

Why are the reaction conditions for the Haber process chosen?

A

They’re chosen to favour the forward reaction and to make the largest amount of product as cheaply as possible

43
Q

What are the conditions for the Haber process?

A

450 degrees, pressure of 200 atmospheres and an iron catalyst

44
Q

How does increasing the temperature affect the position of equilibrium?

A

Equilibrium position shifts in the endothermic direction (transfers energy from surroundings, cooling the surroundings down)

45
Q

How does decreasing the temperature affect the position of equilibrium?

A

Equilibrium position shifts in the exothermic direction (transfer energy to the surroundings which heats them up)

46
Q

How does increasing the gas pressure affect the position of equilibrium?

A

Equilibrium position shifts in direction with fewer gas molecules (this will reduce the pressure)

47
Q

How does decreasing the gas pressure affect the position of equilibrium?

A

Equilibrium position shifts in direction that forms more gas molecules (increase pressure)

48
Q

How does increasing the concentration affect the position of equilibrium?

A

Equilibrium position shifts in the direction that uses up the substance that’s been added

49
Q

How does decreasing the concentration affect the position of equilibrium?

A

Equilibrium position shifts in the direction that forms more of the substance that’s been removed

50
Q

What are the properties of transition metals?

A

Malleable (hammered or rolled without shattering)
Ductile (stretched out)
Good conductors of electricity
Shiny when polished

51
Q

Why is iron used to make buildings/bridges/ships e.t.c?

A

It is malleable and strong

52
Q

Why is copper used to make electrical Wires?

A

It is ductile and a good conductor of electricity

53
Q

What chemical properties do transition metals have (compared to group 1 and 2 metals)

A

High melting points

High densities

54
Q

What else do transition metals normally look like?

A

They’re normally coloured e.g. iron (111) oxide is brown

They’re normally used as catalysts e.g. iron is the catalyst that manufactures ammonia by the Haber process

55
Q

What happens when metals react with oxygen in the air?

A

They oxidise to form metal oxides

56
Q

What happens when reactive metals react with oxygen in the air?

A

They oxidise rapidly when their freshly cut

57
Q

What happens when unreactive metals e.g. gold react with oxygen in the air?

A

They oxidise slowly

Gold e.t.c may not react with oxygen at all

58
Q

How can rusting be prevented?

A

Keeping air away by storing the metal in a (unreactive) atmosphere of nitrogen or argon

59
Q

How else can rusting be prevented (water)?

A

By prevent water from reaching it

For example, a desiccant powder that absorbs water vapour

60
Q

What are some simple ways to prevent rusting?

A

Painting, oiling, greasing or coating with plastic

61
Q

What is sacrificial protection?

A

Doesn’t rely on keeping air or water away
A piece of magnesium or zinc is attached to the iron/steel object
Magnesium and zinc oxidise more easily than iron so the oxygen reacts with the piece of magnesium/zinc rather than the iron/steel
This continues until the sacrifices metal corrodes away

62
Q

Why does a metal oxides more easily than others?

A

The more reactive a metal is, the more easily oxidised it becomes and the more easily it loses its electrons

(OxidAtion is loss)

63
Q

What is electroplating?

A

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

64
Q

Why is it good for jewellery?

A

Gold and silver are attractive but v expensive so solider or gold can be electroplated onto cheaper metals e.g. copper which produces attractive jewellery but for cheaper

65
Q

How may it improve a metal object’s ability to resist corrosion?

A

Chromium is a transition metal that resists corrosion
Objects e.g vehicle parts that are made from steel may be ‘chrome plated’ using electroplating
The thin layer of chromium stops air and water from reaching the steel below, preventing rusting

66
Q

Why will cables and electronic equipment use gold-plated connectors?

A

Gold is the third best electrical conductor (after silver and copper) however it doesn’t tarnish unlike silver and copper

67
Q

What do you need to electroplate an object?

A 
An anode (positively charged electrode)
A cathode (negatively charged electrode)
An electrolyte (solution contains ions of the plating metal)
68
Q

How is an metal electroplated (e,g. Copper ring with silver)?

A

A direct current flows through the electrodes and the electrolyte
The 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 lose electrons to become silver ions which go into the electrolyte
Longer the current flow, the thicker the layer of silver on copper ring

69
Q

What is galvanising?

A

Coating iron/steel objected with zinc

70
Q

How does this work?

A

The thin layer of zinc improves corrosion resistance by stopping the water reaching the iron/steel and acts as a sacrificial metal
This sacrificial protection carries on even if the zinc layer is damaged

71
Q

He can something be galvanised?

A

Carried out by electroplating

Dipping the object in molten zinc

72
Q

How are food cans protected?

A

Their made from steel but their inner surface is protected from rusting by electroplating with tin
Tin doesn’t react with air or water at room temp

73
Q

However what happens if the tin layer is damaged?

A

The steel can will rust faster

This is because iron is more reactive than tin so the iron Will act as a sacrificial metal to protect the tin

74
Q

What is an alloy?

A

A mixture of a metal element with one or more other elements

75
Q

What are alloy steels?

A

They are made deliberately by adding other elements to iron

76
Q

Why do stainless steels revisit rusting?

A

They contain chromium which reacts with the oxygen in the air to form chromium oxide.
This layer is thick enough to stop air and water but thin enough to be transparent
If the layer is scratched, more chromium reacts to replace the layer

77
Q

How do you make the metal/alloy stronger or harder?

A

You increase the carbon content of steel

78
Q

What is mild steel (low carbon content) used for?

A

Building material and car parts

79
Q

Why do car manufactures use strong steels?

A

Although their more difficult to press into shape, car manufacturers use them to produce strong but relatively light weight car bodies

80
Q

How are the atoms arranged in a solid pure metal (no alloys)?

A

They are all the same size and are arranged regularly and in layers
These layers move past each other of enough force is applied
This is why metals are malleable and ductile

81
Q

How are atoms arranged in an alloy?

A

The atoms of other elements may be different sizes
They distort the regular structure making it more difficult for layers to slide past each other
This is why they are stronger

82
Q

What are the properties of gold and copper?

A

Both resist corrosion
Both malleable and ductile and good conductors
Both good for electrical wiring
Gold is more expensive so copper is chosen for most electrical wiring
Gold is used in tiny amounts e.g. memory chips

83
Q

How do alloys have more useful properties than the elements 5ey contain?

A

Brass is alloy of copper and zinc
Copper and brass both resist corrosion
Copper is a better electrical conductor but brass is a lot stronger
So brass is preferred when it comes to electrical plug pins

84
Q

What does a low density mean?

A

Light weight

Chemistry Paper 1 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions