Brainscape's Knowledge GenomeTM

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


See full index

GCSE Chemistry > C4 - Chemical Changes > Flashcards

C4 - Chemical Changes Flashcards

1
Q

What colour are acids on the pH scale?

A

Red / orange

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

What colour are alkalis on the pH scale?

A

Blue / purple

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

What does pH mean?

A

Power of hydrogen- a measure of the concentration of H+ ions in the solution.

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

What are 4 measuring instruments for pH?

A
  • Litmus paper
  • Phenolphthalein
  • Universal indicator
  • pH probe (goes in the solution) attached to a pH meter.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What colour does blue litmus paper turn in acids?

A

Red

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

What colour does blue litmus paper turn in alkalis?

A

Stays blue

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

What colour does red litmus paper turn in acids?

A

Stays red

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

What colour does red litmus paper turn in alkalis?

A

Blue

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

What is useful about universal indicator?

A

It matches a shade on the pH scale.

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

What is the benefit of measuring pH digitally?

A

It is more accurate and gives numerical values rather than a colour, which is harder to interpret.

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

What is the equation for neutralisation?

A

Acid + base = salt + water

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

How can neutralisation be shown in terms of hydrogen and hydroxide ions?

A

H+(aq) + OH-(aq) ⇒ H20(l)

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

What is the formula of sulfuric acid?

A

H2SO4

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

What is the formula of nitric acid?

A

HNO3

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

What is the formula of hydrochloric acid?

A

HCl

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

What is the formula of copper hydroxide?

A

Cu(OH)2

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

What is the formula of sodium hydroxide?

A

NaOH

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

What is the formula of magnesium oxide?

A

MgO

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

What makes a substance acidic?

A

H+ ions

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

What salt does sulfuric acid produce in neutralisation reactions?

A

Sulphate

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

What salt does hydrochloric acid produce in neutralisation reactions?

A

Chloride

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

What salt does nitric acid produce in neutralisation reactions?

A

Nitrate

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

What do acids donate in neutralisation reactions?

A

H+ ions

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

Why are strong acids more reactive than weak acids of the same concentration? What does this mean?

A

They dissociate more H+ ions so the rate of reaction is quicker

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

What makes an acid strong?

A

Strong acids ionise- dissociate hydrogen ions- completely in water. The percentage of dissociated H+ ions is higher per litre

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

What does a value of 1 on the pH scale mean in terms of hydrogen ions?

What does an increase in 1 mean?

A

There is one mole of dissociated hydrogen ions per litre of solution.

The concentration of dissociated H+ ions has decreased by a factor of 10.

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

Is the pH of a stronger acid lower or higher than of a weaker acid (for the same concentration in a solution)?

A

Lower

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

Name 3 strong acids

A
  • Sulfuric
  • Nitric
  • Hydrochloric acid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Name 4 weak acids

A
  • Ethanoic
  • Citric
  • Tartaric
  • Carbonic acid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is the difference between bases and alkalis?

A

Alkalis are soluble metal hydroxides. Bases are metal oxides or hydroxides and can neutralise acids. All alkalis are bases but not all bases are alkalis.

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

Potassium hydroxide + hydrochloric acid -> ______ + ______

A

Potassium chloride + water

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

What reacts to form copper chloride and water?

A

Hydrochloric acid and copper oxide.

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

What is the balanced symbol equation for the reaction between potassium hydroxide and sulfuric acid?

A

2KOH + H2SO4 → K2SO4 + 2H2O

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

What is the reactivity series?

A

It lists metals in order of their reactivity towards other substances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the order of the elements in the reactivity series, from most to least?

A

Potassium, sodium, lithium, calcium, magnesium, aluminium, carbon, zinc, iron, hydrogen, copper

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What determines metals’ reactivity?

A

How easily they lose electrons (oxidise).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Acid + metal -> ______ + ______

A

Salt + hydrogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

______ + ______ -> salt + hydrogen

A

Acid + metal

39
Q

Acid + metal → salt + hydrogen. What indicates the speed of this reaction?

A

The rate at which bubbles of hydrogen are given off, or the temperature change.

40
Q

Metal + water -> ______ + ______

A

Metal hydroxide + hydrogen

41
Q

______ + ______ -> metal hydroxide + hydrogen

A

Metal + water

42
Q

Which metals will react with water?

A

The more reactive ones: potassium, sodium, lithium and calcium.

43
Q

What is tarnishing?

A

Rusting - what happens to the surface of metals when they react with water.

44
Q

What is oxidation?

A

1) A loss of electrons

2) When a metal reacts to bond with oxygen, forming an oxide.

45
Q

What is reduction?

A

1) A gain in electrons

2) When a metal breaks a bond with oxygen.

46
Q

How can metals be tested to see how reactive they are in comparison to others?

A

They can be tested in dilute acids

47
Q

What does the reactivity of a metal depend upon?

A

Its tendency to give away outer electrons and form positive ions- oxidise

48
Q

Why do metals have to be extracted?

A

Metals react with oxygen to form oxides (oxidation), forming ores from which they have to be extracted

49
Q

What is the name given to a reaction that separates a metal from its oxide?

A

A reduction reaction

50
Q

Acid + metal oxide -> ______ + ______

A

salt + water

51
Q

______ + ______ -> salt + water

A

Acid + metal oxide/hydroxide

52
Q

Acid + metal hydroxide -> ______ + ______

A

salt and water

53
Q

Acid + metal carbonate -> ______ + ______ + ______

A

salt + water + carbon dioxide

54
Q

______ + ______ -> salt + water + carbon dioxide

A

Acid + metal carbonate

55
Q

Hydrochloric acid + sodium carbonate -> ______ + ______ + ______

A

sodium chloride + water + carbon dioxide

56
Q

Give the equation for the oxidation of magnesium.

A

2Mg + O2 -> 2MgO

57
Q

Which metals can be extracted from their ores chemically by reduction with carbon?

A

Metals below carbon in the reactivity series- zinc, iron, copper.

58
Q

How do reduction reactions work?

A

Carbon reacts with a metal oxide to produce carbon dioxide and the pure metal. This only works if carbon is more reactive than the metal.

59
Q

Describe the practical: making soluble salts using an insoluble base.

A

1) Fill a beaker with boiling water (heat gives energy which will speed up the reaction).
2) Measure 10ml of sulfuric acid into a test tube. Put the test tube into the beaker of water.
3) Allow the acid to heat up before adding copper oxide, which is an insoluble base.
4) The sulfuric acid and copper oxide react, producing a blue salt solution. Excess copper oxide sinks to the bottom.
5) Filter the salt solution from the excess copper oxide- this makes a filtrate.
6) Bring the solution almost to the boil over a bunsen burner, which makes the solution more concentrated (some water boils off) and gives it a higher temperature gradient so that more crystals form.
7) Place the solution into a petri dish; after time, it will become crystalline.

60
Q

How can the reactivity of metals be tested?

A

1) Reacting them with acids: the violence indicates the metal’s reactivity. Increasing heat and concentration of acid can make the reaction faster. The rate of reaction is indicated by the rate at which hydrogen bubbles are released.
2) Reacting them with acid/water and measuring the temperature change. Temperature change will be greater with more reactive metals. Controls should be the time period, the mass and the surface area of the metal.

61
Q

Give the balanced symbol equation for the extraction of iron by reduction with carbon.

A

2Fe2O3 + 3C → 4Fe + 3CO2

62
Q

Which metals can be extracted by reduction with carbon?

A

Those less reactive than carbon, because carbon needs to bond with the oxygen. These are zinc, iron and copper.

63
Q

Why has gold been mined for longer throughout history than other metals?

A

It is found in its elemental form, due to its low reactivity; it does not oxidise to form ores.

64
Q

A gain of electrons =

A

Reduction

65
Q

A loss of electrons =

A

Oxidation

66
Q

What are redox reactions and why do they have this name?

A

A more reactive metal is put into the solution of a less reactive metal, which is displaced from its compound. re=reduction and ox= oxidation; these happen at the same time, hence redox.

67
Q

Redox reactions are the same as…

A

Displacement reactions.

68
Q

In displacement reactions, it’s always the metal ___ that is reduced (gains electrons) and the metal ___ that is oxidised (loses electrons).

A

1) Ion

2) Atom

69
Q

What are spectator ions?

A

Ions which don’t change in a reaction

70
Q

Write the ionic equation for this displacement reaction:

Iron sulfate + zinc →zinc sulfate + iron

A

1) Write symbol equation, including ions:

FeSO4(s) + Zn(aq) → ZnSO4(aq) + Fe(s)

Fe2+SO42- + Zn → Zn2+SO42- + Fe

2) Take out and ignore the spectator ion: SO42-
3) Write the ionic equation, including only the atoms/ions which are reduced or oxidised:

Fe2+ + Zn → Zn2+ + Fe

4) The iron ions are reduced by the zinc atoms.
5) The zinc atoms are oxidised by the iron ions.

71
Q

What does electrolysis mean?

A

Splitting up with electricity

72
Q

What is the negative electrode?

A

Cathode

73
Q

What is the positive electrode?

A

Anode

74
Q

What is an electrolyte?

A

A molten or dissolved ionic compound.

75
Q

What type of power supply is used for electrolysis?

A

D.C. (direct current)

76
Q

Why is electrolysis necessary for extracting some metals from their ores?

A

Some are too reactive for displacement reactions (more reactive than carbon).

77
Q

What are ores?

A

Compounds in which most metals exist, combined with other elements, typically oxygen or sulphur

78
Q

What happens in electrolysis?

A

An electric current is passed through an electrolyte. Each ion present is attracted to the electrode (charged metal plate) with an opposite charge. Ions are reduced/oxidised to become pure, uncharged elements

79
Q

Positive ions will move towards the ___ and are ___

A

1) Cathode

2) Reduced

80
Q

Negative ions will move towards the ___ and are ___.

A

1) Anode

2) Oxidised

81
Q

Why is cryolite added to aluminium oxide during electrolysis?

A

It lowers the melting point of aluminium, reducing the energy cost

82
Q

Give the half equation for chloride ions at the anode

A

2Cl- → Cl2 + 2e-

83
Q

Is aluminium oxidised or reduced during electrolysis?

A

All metals are reduced

84
Q

Is chlorine oxidised or reduced during electrolysis?

A

All non-metals are oxidised

85
Q

What is the downfall of electrolysis?

A

It is expensive because it requires lots of energy to both produce the current and heat the ionic compound

86
Q

What is different about electrolysis in aqueous solutions?

A

There are ions in the water too, which may react with the electrodes, depending on the reactivity of ions in the electrolyte

87
Q

What is the rule for the reaction at the cathode in electrolysis of aqueous solutions?

A

Metal and H+ ions are present.

If hydrogen is less reactive than the elemental form of the metal, hydrogen gas is produced.

If hydrogen is more reactive, a solid layer of the pure metal forms on the cathode.

Whatever is less reactive reacts with the cathode

88
Q

What is the rule for the reaction at the anode in electrolysis of aqueous solutions?

A

OH- and non-metal ions are present at the anode.

If halide (Cl-, Br-, I-) ions are present, halogens will be produced.

If not, oxygen gas and water will form

89
Q

What are titrations?

A

Experiments which allow you to find the exact volumes of two solutions needed for them to react completely.

Can be used to find the unknown concentration of an acid/alkali, by finding the volume of this needed to neutralise a volume of alkali/acid of known concentration.

90
Q

Describe how you would carry out a titration to find the concentration of an alkali needed to neutralise a volume of an acid of known concentration

A

1) Add a set volume of the alkali to a conical flask using a pipette and pipette filler, then add 3 drops of single indicator (phenolphthalein/litmus/methyl orange).
2) Wearing safety goggles, use a funnel to fill a burette with the acid of known concentration. Record the volume in the burette.
3) Use the burette to add the acid to the alkali a bit at a time, regularly swirling the flask. When all the alkali has been neutralised, the indicator changes colour. When this point is nearing, add only a drop at a time.
4) Once the colour change has occurred, record the final volume of acid in the burette and subtract it from the initial volume to find the volume of acid needed to neutralise the alkali.
5) Repeat steps 1-5 three times to increase the accuracy; your results should be within 0.1cm3 of each other. Omit any anomalous results and calculate the mean volume.
6) Calculate the concentration of the alkali (moles of acid = conc. x volume. Use ratios from balanced symbol equation to find moles of alkali. Conc. of alkali = moles/volume)

91
Q

Why are single (rather than universal) indicators used for titrations?

A

You want to see a sudden and definitive colour change at the point when the acid/alkali has been neutralised

92
Q

What colour does phenolphthalein turn in:

1) Acids?
2) Alkalis?

A

1) Acids: colourless

2) Alkalis: pink

93
Q

What colour does litmus turn in:

1) Acids?
2) Alkalis?

A

1) Acids: red

2) Alkalis: blue

94
Q

What colour does methyl orange turn in:

1) Acids?
2) Alkalis?

A

1) Acids: red

2) Alkalis: yellow

GCSE Chemistry (10 decks)

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