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Chemistry GCSE > Topic 3 - Chemical Changes > Flashcards

Topic 3 - Chemical Changes Flashcards

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1
Q

What do acids form in water?

A

H+ ions

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2
Q

What does the higher the conc of H+ mean?

A

The more acidic the solution is

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3
Q

What do alkalis form in water?

A

OH- ions

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4
Q

What does the higher the conc of OH- mean?

A

The more alkaline the solution is

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5
Q

What is a base?

A

A substance which reacts with an acid to produce a salt and water

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6
Q

What is an indicator?

A

A dye that changes colour depending on whether it’s above or below a certain pH

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7
Q

State the colour of litmus in acid?

A

Red

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8
Q

State the colour of litmus in neutral?

A

Purple

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9
Q

State the colour of litmus in alkaline?

A

Purple

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10
Q

State the colour of methyl orange in acid?

A

Red

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11
Q

State the colour of methyl orange in neutral?

A

Yellow

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12
Q

State the colour of methyl orange in alkaline?

A

Yellow

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13
Q

State the colour of phenolphthalein in acid

A

Colourless

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14
Q

State the colour of phenolphthalein in neutral?

A

Colourless

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15
Q

State the colour of phenolphthalein in alkaline?

A

Pink

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16
Q

What does neutralisation produce?

A

Salt and water

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17
Q

State the neutralisation ionic equation?

A

H+ + OH- -> H2O

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18
Q

The pH of an unknown solution is 2

Is the solution acidic or alkaline?

A

Acidic

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19
Q

How do you investigate the neutralisation reaction of CaO and HCl?

A

Measure out HCl and CaO

Add and then record pH and repeat

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20
Q

What does dissociating H+ mean?

A

Splitting up to produce hydrogen ions

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21
Q

What are strong acids?

A

Acids that almost completely ionise in water

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22
Q

What are weak acids?

A

Acids that partially ionise in solution

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23
Q

What type of reaction is the ionisation of a weak acid?

A

A reversible one

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24
Q

What are alkalis?

A

Soluble bases

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25
Q

What does acid strength tell you?

A

What proportion of the acid molecules ionise in water

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26
Q

What does acid strength tell you?

A

What proportion of the acid molecules ionise in water

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27
Q

What does acid concentration tell you?

A

How much acid there is in a volume of water (how watered down the acid is)

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28
Q

Describe a dilute acid?

A

An acid with a small number of acid molecules compared to the volume of water

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29
Q

Describe a concentrated acid?

A

An acid with a large number of acid molecules compared to the volume of water

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30
Q

What does acid concentration not describe?

A

The number of molecules that produce hydrogen ions

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31
Q

How does a decrease in 1 pH affect a solutions H+ ions level?

A

1 less pH will mean 10x more H+ ions

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32
Q

A solution with a hydrogen ion concentration of 0.001 M has a ph of 3
What would happen to the pH if you increased the hydrogen ion concentration to 0.01 M

A

The H+ concentration has increased by 10x therefore the pH would decrease by 1
3 - 1 = 2

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33
Q

Explain the difference between a strong acid and a weak acid?

A

A strong acid ionises almost completely in water whilst a weak acid only partially ionises in water

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34
Q

A student added a strong acid to a solution with a pH of 6
The new solution had a pH of 3
State whether the concentration of H+ had increased or decreased and by what factor

A

Increased by x10^3

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35
Q

Acid + Metal Oxide =?

A

Salt + Water

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36
Q

Acid + Metal Hydroxide =?

A

Salt + Water

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37
Q

Acid + Metal =?

A

Salt + Hydrogen

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38
Q

Acid + Metal Carbonate =?

A

Salt + Water + Carbon Dioxide

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39
Q

How can you test for hydrogen?

A

A lit splint making a ‘squeaky pop’

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40
Q

Where does the pop in the ‘squeaky pop’ test come from?

A

The hydrogen burning with the oxygen in the air

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41
Q

How do you test for carbon dioxide?

A

Bubble the gas through lime water and if the water goes cloudy, Carbon dioxide is present

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42
Q

Write a symbol equation for the reaction of hydrochloric acid with calcium carbonate?

A

HCl + CaCO3 -> CaCl2 + H20 + CO2

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43
Q

Write a balanced symbol equation for the reaction of hydrochloric acid with calcium carbonate?
HCl + CaCO3 -> CaCl2 + H20 + CO2

A

2HCl + CaCO3 -> CaCl2 + H20 + CO2

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44
Q

What salt’s are always soluble?

A

Sodium, potassium, ammonium and nitrates

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45
Q

What chlorides are insoluble?

A

Silver and lead

46
Q

What sulfates are insoluble?

A

Lead, Barium and Calcium

47
Q

What carbonates/hydroxides are soluble?

A

Sodium, Potassium and Ammonium

48
Q

What do you need to pick when making salts via precipitation?

A

Two soluble salts that react together to form an insoluble salt

49
Q

Explain why, if soluble salts are prepared from an acid and an
insoluble reactant an excess of the reactant is added?

A

To ensure all of the acid has reacted allowing the solution to be made of the products and the insoluble excess reactant which can easily be filtered

50
Q

Suggest two reactants you could use to form barium sulfate in a precipitation reaction?

A

Barium Nitrate + Sodium Sulfate

51
Q

When given a insoluble salt and asked for two soluble salts that could be used, whats a easy way to answer without having to ensure they are soluble

A

_____ Nitrate + Sodium _____

52
Q

When reacting acid with a base, why is it heated?

A

To speed up the reaction

53
Q

When adding base to acid, when can you tell all the base has been used?

A

The base no longer reacts with the acid, instead it sits at the bottom of the flask

54
Q

How do you neutralise an acid with an alkali?

A

Titration

55
Q

How do you do titration?

A

You do a rough titration and add acid into a flask and indicator, then add alkali until the end point is reached
Then repeat, without indicator, at much slower incriments and then slowly evapourate off some of the water and then leave the solution to crystallise

56
Q

Iron Nitrate is a soluble salt that can be made from iron oxide and nitric acid
Suggest which method you should use?

A

Excess base

57
Q

What two things does elecrolysis involve?

A

Reduction and oxidation

58
Q

What are electrolytes?

A

Molten or aqeous ionic compounds

59
Q

What type of current must electrolysis have?

A

Direct Current

60
Q

Describe electrolysis

A

A process where electrical energy, from DC, decomposes electrolytes

61
Q

What ions migrate to the cathode?

A

Positively charged cations

62
Q

What ions migrate to the anode?

A

Negatively charged anions

63
Q

What charge is the cathode?

A

Negative

64
Q

What charge is the anode?

A

Positive

65
Q

Where would Mg2+ go to in electrolysis?

A

The cathode

66
Q

Where would Cl- go to in electrolysis?

A

Anode

67
Q

What ions are oxidised in electrolysis?

A

Anions

68
Q

What ions are reduced in electrolysis?

A

Cations

69
Q

What happens to the cations in electrolysis?

A

They go to the cathode and reduce

70
Q

What happens to the anions in electrolysis?

A

They go to the anode and oxidise

71
Q

Give eamples of inert electrodes?

A

Graphite and platinum electrodes

72
Q

What is formed in copper chloride molten?

A

Copper at cathode

Chlorine gas at anode

73
Q

What is formed in sodium chloride molten?

A

Sodium at cathode

Chlorine gas at anode

74
Q

How do you electrolyse a molten ionic substance?

A

Put the solid substance in a crucible and melt it

Dip two electrodes into the liquid and then connect the electrodes to a power supply

75
Q

At which electrode does oxidation happen?

A

Anode

76
Q

How do you electrolyse a solution?

A

Clean electrodes with emery paper
Add electrodes into solution
And turn on the circuit

77
Q

Why can’t an ionic solid be electrolysed?

A

Because the ions are in fixed positions and can’t move

78
Q

How is what appears at the cathode get decided in a solution?

A

Based on whether the metal is more reactive than the hydrogen

79
Q

If a metal is more reactive than hydrogen, what will appear at the cathode?

A

The hydrogen

80
Q

If a metal is less reactive than hydrogen, what will appear at the cathode?

A

The metal

81
Q

How do you remember what appears at the anode?

A

If its an ate, It “ate”‘n’t that one
If its an ide, “Ide” bet it’s that one
If its an halide, “Ide” bet on “hal” it’s that one

82
Q

When a solution of sodium chloride is electrolysed where and what is formed?

A

Hydrogen at cathode

Chlorine gas at annode

83
Q

When a solution of sodium sulfate is electrolysed where and what is formed?

A

Hydrogen at cathode

Oxygen at cathode

84
Q

When a solution of sulfuric acid (H2SO4) is electrolysed where and what is formed?

A

Hydrogen at cathode

Oxygen at anode

85
Q

What is the half equation at an anode when oxygen is produced?

A

4OH- -> O2 + 2H2O + 4e-

86
Q

An aqueous solution of copper bromide, CuBr2, is electrolysed using inert electrodes
Give the half equation to show the reaction occurring at the anode

A

2Br- - e- -> Br2

87
Q

What four different ions does copper sulfate (aq) contain?

A

Cu2+, H+, OH- and SO4(2-)

88
Q

What do you get when you electrolyse copper sulfate solution with inert electrodes?

A

Copper at the cathode

Oxygen at the anode

89
Q

What do gases appear as in electrolysis?

A

Bubbles

90
Q

What happens when you electrolyse copper sulfate with copper electrodes?

A

The mass of the anode will decrease whilst the mass of the cathode will increase

91
Q

Why does the mass of the anode will decrease whilst the mass of the cathode will increase when electrolysing copper sulfate with copper electrodes?

A

The copper from the anode is being transferred to the cathode

92
Q

What should you ensure before weighing electrodes?

A

The electrodes are dry

93
Q

Why must the electrodes be dry when weighing?

A

To increase the accuracy of the results

94
Q

What happens to the rate of electrolysis as you increase current?

A

It increases

95
Q

How does the electrical supply work in the electrolysis of copper sulfate with copper cathodes?

A

Pulls electrons off the copper anode

Offers electrons at the cathode to nearby copper ions

96
Q

What happens to the impure copper annode during electrolysis?

A

It is oxidised and dissolves into the electrolyte to form copper ions

97
Q

What happens to the copper ions during electrolysis?

A

They are reduced at the cathode and add to it as a layer of pure copper

98
Q

What happens to the impurities from the impure copper anode during electrolysis?

A

They sink to the bottom forming a sludge

99
Q

Explain how electrolysis is used to purify copper for use in electrical circuits?

A

The anode is a large thick pick of impure copper whilst the cathode is a thin piece of pure copper. During the electrolysis the supply pulls electrons off the atoms so they dissolve and form copper ions. The copper ions migrate to the cathode where the yaccept electrons to reform copper atoms and coat the cathode with a pure layer of copper

100
Q

State what colours; litmus, methyl orange and phenolpthalein will turn in acidic solutions?

A

Litmus - Red
Methyl Orange - Red
Phenolpthalein - Colourless

101
Q

What does a pH curve look like?

A 
/-----------
             |
             | 
            /
---------/
102
Q

Write an equation to show how ethanoic acid acts as a weak acid?

A

CH3COOH ⇌ CH3COO- + H+

103
Q

If you increase the hydrogen ion conc of a solution by a factor of 10, what will happen to the pH of the solution?

A

Decrease by 1

104
Q

Write a chemical equation to show how HCl reacts with CuO?

A

2HCl + CuO -> CuCl2 + H2O

105
Q

Describe a test you could carry out to test for hydrogen gas?

A

A lighted splint making a squeaky pop

106
Q

What would you expect to see if you bubbled carbon dioxide through limewater?

A

It will turn cloudy

107
Q

List three insoluble sulfates

A

Lead, barium and calcium

108
Q

Name two soluble hydroxides?

A

Potassium and sodium

109
Q

Towards which electrode do the anions move?

A

The anode

110
Q

Why do the masses of non-inert electrodes change during electrolysis?

A

The non-inert anode loses its mass to the non-inert cathode

Chemistry GCSE (10 decks)

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