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GCSE Chemistry > Chemical Changes > Flashcards

Chemical Changes Flashcards

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1
Q

Oxidation is the… of electrons

A

Loss

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2
Q

Reduction is the.. of electrons

A

Gain

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3
Q

How are highly reactive metals extracted

A

Electrolysis

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4
Q

Why are gold and silver found naturally as elements in the earth’s crust

A

They are unreactive

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5
Q

What is an ore

A

A rock containing a metal compound

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6
Q

In terms of oxygen what is oxidation

A

Oxygen added

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7
Q

In terms of oxygen what is reduction

A

Loss of oxygen

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8
Q

What type of metals can be extracted through reduction with carbon

A

Ones less reactive than carbon e.g iron, zinc and lead
(Carbon displaces them from their compound)

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9
Q

What is a spectator ion

A

Ion that is unchanged in a reaction

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10
Q

What does OIL RIG stand for

A

Oxidation is loss
Reduction is gain
Both in terms of electrons (it’s the other way round for oxygen)

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11
Q

2 chemical properties of most transition metals

A

Form ions with different charges
React slowly/ not at all with halogens, oxygen and water

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12
Q

What is electrolysis

A

Using electricity to extract elements from their compound

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13
Q

What is the electrolyte

A

The liquid/ solution containing ions and can conduct electricity

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14
Q

In electrolysis what is the electric current passed through

A

The electrolyte (liquid/ solution containing the ions)

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15
Q

Name for positive electrode

A

Anode

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16
Q

Name for negative electrode

A

Cathode

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17
Q

Can solid ionic compounds conduct electricity

A

No
Ions aren’t free to move and carry charge
Must be molten/ dissolved in water so ions are free to move

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18
Q

Why must the ionic compound in electrolysis be molten/ dissolved in water

A

Means ions are free to move and can carry charge (conduct electricity) and move to the electrodes

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19
Q

Which electrode do negative ions move to

A

Positive anode

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20
Q

Which electrode do positive ions move to

A

Negative cathode

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21
Q

What happens at the cathode for molten compounds

A

Cathode= negative so attracts positive metal ions
Metals gain electrons to form pure metal

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22
Q

What happens at the anode for molten compound

A

Anode= positive so attracts negative non-metal ions
Non metal loses electrons and becomes pure non-metal

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23
Q

In electrolysis which out of the metal and non metal forms positive ions, which forms negative

A

Metal- positive ions
Non-metal- negative ions

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24
Q

If sodium chloride undergoes electrolysis what will be formed at each electrode

A

Negative Cathode= sodium (metal)
Positive anode= chlorine (non- metal)

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25
Q

Which requires more energy, electrolysis of molten compounds or aqueos solutions

A

Molten- more energy required to melt ionic compound than dissolve it in water

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26
Q

What type of compound is electrolysis used for

A

Ionic
(must be molten/ dissolved in water)

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27
Q

In the electrolysis of aqueous solutions why aren’t the pure metals always produced

A

Water undergoes ionisation
Hydrogen can be formed at the cathode if less reactive than the metal
Oxygen and water can be formed at the anode from the hydroxide ions if a halide (e.g chlorine, iodine, bromine..) isn’t present

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28
Q

During electrolysis when is hydrogen produced

A

If it is an aqueous solution and the metal is more reactive than hydrogen

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29
Q

During electrolysis when is oxygen produced

A

If it’s an aqueous solution and no halide is present- hydroxide ions lose electrons at anode

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30
Q

When is electrolysis used to extract metals

A

If metal is more reactive than carbon (cannot be reduced by it)

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31
Q

Why is cryolite added to aluminium oxide during electrolysis

A

Lowers melting point- cheaper as less energy required

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32
Q

What are the electrodes made of during electrolysis of molten aluminium oxide

A

Graphite

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33
Q

Why must the graphite electrode be replaced regularly during electrolysis

A

Reacts with oxygen to form carbon dioxide so it’s slowly burnt away

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34
Q

What ions do acids release when dissolved in water

A

H+

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35
Q

What are the 3 main acids

A

Sulfuric acid, nitric acid, hydrochloric acid

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36
Q

True or false, acids and alkalis are both compounds

A

True

37
Q

What ions do alkalis release when dissolved in water

A

OH-

38
Q

True or false, the more H+ there are in a solution then the lower the PH

A

True as H+ is acidic

39
Q

3 examples of strong acids (also the 3 main acids)

A

Hydrochloric
Sulfuric
Nitric

40
Q

What happens to strong acids when they dissolve in water

A

They are completely ionised
Every molecule splits up into ions

41
Q

Which out of strong and weak acids are completely ionised when dissolved in water

A

Strong acids
E.g hydrochloric, nitric and Sulfuric

42
Q

What does completely ionised mean

A

All molecules split up into ions
E.g strong acids when dissolved in water

43
Q

What happens to weak acids when dissolved in water

A

They are partially ionised
Only some of their molecules split up into ions

44
Q

For a given concentration the stronger the acid the….. the pH

A

Lower

45
Q

Which out of strong acids and weak acids are completely ionised and which are partially ionised when dissolved in water

A

Strong= completely ionised (all molecules split up into ions)
Weak= partially ionised (only some molecules split up into ions)

46
Q

Which out of concentrated or dilute acids will have lots of acid in a small volume of water

A

Concentrated
(Dilute acids have little acid in a large volume of water)

47
Q

…acids have lots of acid in a small volume of water

A

Concentrated

48
Q

…acids have little acid in a large volume of water

A

Dilute

49
Q

Describe a dilute strong acid

A

Few acid ions (dilute)
They are completely ionised (strong acid)

50
Q

Describe a concentrated strong acid

A

Lots of acid ions (concentrated)
Completely ionised (strong)

51
Q

Describe a dilute weak acid

A

Few acid ions (dilute)
Partially ionised (weak)

52
Q

Describe a concentrated weak acid

A

Lots of acid ions (concentrated)
Partially ionised (weak)

53
Q

What do acids reacting with metal/ metal compounds form

A

Salts

54
Q

Complete equation
Metal + acid->

A

Salt + hydrogen

55
Q

Complete equation
Metal hydroxide + acid->

A

Salt + water

56
Q

Complete equation
Acid+ metal oxide->

A

Salt + water

57
Q

Complete equation
Acid + metal carbonate->

A

Salt+ water+ carbon dioxide

58
Q

True or false when metal hydroxides and metal oxides react with acid they both form a salt + water

A

True

59
Q

Alkali vs base

A

Both neutralise acids to form water in neutralisation reactions
If they dissolve in water (forming alkali solutions) they’re called alkalis

60
Q

True or false alkalis are a type of base (neutralise acid to form water) that dissolve in water

A

True

61
Q

What does crystallisation produce

A

Solid salt (from an insoluble base)

62
Q

Process of crystallisation

A

Put fixed volume of dilute acid into flask (using measuring cylinder) and heat gently with Bunsen burner
Add small amount of base and stir
Keep adding base until no more reacts (it’s now in excess)
Filter to remove unreacted base
Add remaining solution to evaporation dish and place on top of water bath over Bunsen burner
Water will be evaporated leaving behind salt crystals

63
Q

How can you obtain a solid salt from a solution

A

Crystallisation

64
Q

2 ways PH can be measured and which is more accurate

A

Universal indicator
Probe

Probe more accurate as exact decimal number

65
Q

What does copper oxide look like

A

Black powder

66
Q

When making crystals why should the acid be heated

A

Speeds up reaction

67
Q

For titrations why should you use a pipette not a beaker to measure the fixed volume of the unknown concentration

A

More accurate as it has a better resolution (smaller scale)

68
Q

When carrying out a titration why should you place a white tile under the conical flask

A

To see a clearer colour change

69
Q

What is a concordant result

A

Results within 0.1cm cubed of each other
(When carrying out titrations)

70
Q

Describe a 6 mark method for carrying out a titration (remember in an exam you will have to use information from the question to know which is the ‘known/ unknown’ concentration

A

1) With a pipette measure a fixed volume of unknown into a conical flask (place conical flask on white tile to be able to see clearer colour change)
2) Add 2-3 drops of indicator (methyl orange/ phenolphthalein) to conical flask and swirl
3) Add known to burette with tap off
4) Turn on tap and add the known into the unknown in the conical flask (swirling flask whilst doing so) until a colour change occurs
5) This is the first rough titration and has gone past the ‘end point’
6) Carry out another titration but start adding drop wise as you approach the end point and swirl in between until the color change (neutralisation) has occurred
7) Keep carrying out titrations until you have 3 concordant results (ignore anomalies)

71
Q

When should you stop carrying out titrations

A

Once you have 3 concordant results

72
Q

Describe how to make a pure, dry sample of soluble salt using a dilute acid and insoluble metal oxide/ carbonate) (use information in question as to what metal oxide/ metal carbonate to use and which acid to use)

A

1) measure fixed volume of acid in beaker and gently heat over Bunsen burner until almost boiling
2) Use a spatula to add small amounts of the oxide/ carbonate (powder) to the acid and stir using a glass rod to form a solution
3) keep adding one spatula at a time until the oxide/ carbonate is in excess (when some powder still remains after stirring)
4) Use a filter funnel and filter paper to filter out the insoluble carbonate/ oxide and collect the filtrate (reacted solution) in a conical flask
5) place the solution in an evaporating basin and place on a water bath over a Bunsen burner
6) Stop heating when half the solution has evaporated and crystals have started to form around the edge of the basin
7) Leave the remaining solution in a cool place for 24hrs to allow crystals to form
8) Gently pat crystals dry with paper towel

73
Q

2 hazards of making soluble salts RPA

A

Bunsen burner and hot apparatus
Concentrated acid

74
Q

Possible harm of concentrated acid (hazard) in making soluble salts RPA and safety precaution to address hazard

A

Corrosive and damages skin and clothes.
Use dilute acid and wear goggles

75
Q

Why should a dilute not concentrated acid be used in making soluble salts RPA

A

Concentrated acid is corrosive and can damage skin and clothes

76
Q

Why is the Bunsen burner and hot apparatus a hazard in the making soluble salts RPA and what safety precaution can be taken

A

Tie back hair and roll up sleeves to prevent them catching fire
Do not touch hot equipment to prevent burning yourself

77
Q

For making soluble salts RPA why do you gently heat the acid before adding the oxide/ carbonate

A

Increase rate of reaction
Ensure all oxide/ carbonate will react

78
Q

3 key scientific processes occurring in making soluble salts RPA

A

Filtration (filter out excess oxide carbonate from solution)
Evaporation
Crystallisation (crystals forming)

79
Q

Describe how to carry out the electrolysis of an aqueous solution (in this example use copper chloride)

A

1) Place copper chloride solution Into a beaker
2) place plastic Petri dish over beaker with 2 holes in
3) Insert graphite rod into each hole (electrodes)- electrodes must not be touching or it will produce a short circuit
4) Attach a crocodile clip to each rod and connect them to a low voltage power supply using wire
5) Switch on the power supply with 4V
6) The anode should start to become coated in copper
7) At the anode gas bubbles should appear + smell of chlorine in air
8) Hold a damp piece of blue litmus paper at the anode and it should become bleached (proves that chlorine gas is being formed)

80
Q

What would be different when carrying out the electrolysis of copper chloride compared to sodium chloride (solutions)

A

For copper chloride copper is formed at cathode
For sodium chloride hydrogen is formed so gas bubbles will form at cathode (we can prove that the gas is hydrogen by collecting it and testing it with a lit splint- it should produce a squeaky pop)

For both bubbles of chlorine gas should form at the anode (chlorine can be tested as it should bleach damp blue litmus paper)

81
Q

During electrolysis how can we tell if chlorine has been produced at the anode

A

Bubbles
Smell of chlorine in air
Bleaches damp blue litmus paper

82
Q

In a titration what do you use to measure a fixed volume of the unknown concentration into the conical flask

A

Pipette

83
Q

What does chlorine do to damp blue litmus paper

A

Bleaches it

84
Q

How to test for hydrogen gas

A

Place lit splint in test tube containing gas
If hydrogen is present it will produce a squeaky pop

85
Q

True or false, transition metals form ions with different charges

A

True

86
Q

True or false, transition metals have high melting points

A

True

87
Q

How to collect gas produced in electrolysis

A

Place test tube over electrode (or measuring cylinder is measuring volume)

88
Q

Why blue colour of copper sulphate solution becomes paler in electrolysis

A

Copper ions are removed

GCSE Chemistry (18 decks)

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