Chemical Changes Flashcards
(128 cards)
1
Q
What do metals produce when they react with oxygen?
A
Metal oxides
Metals react with oxygen in the air to form metal oxides in a process known as oxidation.
2
Q
Define oxidation in terms of oxygen.
A
A reaction in which oxygen is added to an element or a compound.
3
Q
Define reduction in terms of oxygen.
A
A reaction in which oxygen is removed from an element or a compound.
4
Q
What is a redox reaction?
A
A reaction involving simultaneous oxidation and reduction.
5
Q
What happens to copper metal when it reacts with oxygen?
A
It is oxidised to produce copper oxide.
6
Q
What is the result of the reaction between zinc oxide and carbon?
A
Zinc is produced as zinc oxide is reduced.
7
Q
What does the reactivity series indicate?
A
The order of metals based on their reactivity.
8
Q
What is the tendency of a metal to lose electrons a measure of?
A
How reactive the metal is.
9
Q
Which non-metals are included in the reactivity series?
A
Carbon and hydrogen.
10
Q
Fill in the blank: The reactivity series mnemonic is ‘Please send lions, cats, monkeys and cute zebras into ______.’
A
hot countries signed Gordon.
11
Q
Which group of metals is most reactive with water?
A
Group 1 metals.
12
Q
What products are formed when metals react with cold water?
A
Metal hydroxide and hydrogen gas.
13
Q
What type of reaction occurs when metals react with dilute acids?
A
A salt and hydrogen gas are produced.
14
Q
Which metals do not react with dilute acids?
A
Metals below hydrogen in the reactivity series.
15
Q
True or False: Aluminium reacts readily with water.
A
False.
16
Q
What is the role of carbon in the extraction of metals?
A
A reducing agent to remove oxygen from metal oxides.
17
Q
What is a metal ore?
A
A rock that contains enough metal to make extraction worthwhile.
18
Q
How are unreactive metals typically found?
A
As native metals in their uncombined state.
19
Q
What determines the method of extraction for metals?
A
The position of the metal in the reactivity series.
20
Q
What is produced when a metal oxide is reduced by carbon?
A
The metal and carbon dioxide.
21
Q
How do more reactive metals behave in displacement reactions?
A
They displace less reactive metals from their compounds.
22
Q
Fill in the blank: The extraction method for potassium is ______.
A
extracted by electrolysis.
23
Q
What is oxidation in terms of electrons?
A
When a substance loses electrons.
24
Q
What is reduction in terms of electrons?
A
When a substance gains electrons.
25
What happens in a displacement reaction?
A more reactive metal displaces a less reactive metal.
26
What is it called when a substance gains an electron?
It is reduced
## Footnote
This is a key concept in redox reactions.
27
What are spectator ions?
Ions that appear unchanged on both sides of a reaction
## Footnote
In the ionic equation, SO42– is a spectator ion.
28
What does the half-equation Fe → Fe2+ + 2e– illustrate?
Oxidation
## Footnote
Iron loses electrons to become a positive ion.
29
What does the half-equation Cu2+ + 2e– → Cu illustrate?
Reduction
## Footnote
Copper gains electrons to become a neutral atom.
30
What is the principle represented by 'OIL RIG'?
Oxidation Is Loss, Reduction Is Gain of electrons
## Footnote
This mnemonic helps remember the definitions of oxidation and reduction.
31
How can you verify the correctness of half equations?
Check that the number of electrons on either side is the same
## Footnote
This ensures charge balance in the reaction.
32
What is the general equation for the reaction of a metal with an acid?
metal + acid ⟶ salt + hydrogen
33
Which metals can react with dilute acids?
Only metals above hydrogen in the reactivity series
34
What is a redox reaction?
A reaction involving both reduction and oxidation occurring simultaneously
35
What is produced in an acid-base neutralisation reaction?
Salt and water
36
What do you call a base that dissolves in water?
Alkali
37
What is the result when a metal carbonate reacts with an acid?
Salt, water, and carbon dioxide
38
What indicates the presence of carbon dioxide gas in a reaction?
The limewater turns milky or cloudy
39
What ions does hydrochloric acid produce in salts?
Chloride ions (Cl–)
40
How are the names of salts derived?
The first part comes from the metal/base, and the second part comes from the acid
41
What is the formula for magnesium phosphate?
Mg3(PO4)2
42
What is the method for preparing a soluble salt from an insoluble base?
* Add insoluble base in excess to acid
* Filter to remove excess base
* Evaporate the solution to form crystals
43
Why is the insoluble base added in excess during the preparation of a soluble salt?
To ensure all of the acid has reacted and avoid dangerous concentration
44
What are the steps involved in preparing a soluble salt?
* Warm dilute acid
* Add insoluble oxide and stir
* Filter to remove excess base
* Heat to evaporate water
* Allow to crystallise
45
What do acids produce when dissolved in water?
Positively charged hydrogen ions (H+)
46
What pH values do bases have?
pH values above 7
47
What is the outcome of an acid reacting with a metal oxide?
Metal salt and water
48
What is the effect of adding acids to water?
They form positively charged hydrogen ions (H+)
49
What is the effect of adding alkalis to water?
They form negative hydroxide ions (OH–)
50
What does the pH scale measure?
The amount of hydrogen ions present in a solution
51
What is the pH range for acids?
Below 7
52
What is the pH range for alkalis?
Above 7
53
What pH value is considered neutral?
7
54
What pH range indicates a strong acid?
pH 1-3
55
What pH range indicates a weak acid?
pH 4-6
56
What pH range indicates a weak alkali?
pH 8-11
57
What pH range indicates a strong alkali?
pH 12-14
58
How can pH be measured?
Using a digital pH meter or an indicator
59
What is a universal indicator?
A wide range indicator that gives an approximate pH value
60
What does a neutralisation reaction involve?
An acid reacting with an alkali to produce water
61
What is the net ionic equation for neutralisation?
H+ (aq) + OH– (aq) → H2O (l)
62
What do strong acids do in water?
Fully ionise in water
63
Give examples of strong acids.
* Hydrochloric acid (HCl)
* Nitric acid (HNO3)
* Sulfuric acid (H2SO4)
64
What characterizes weak acids?
They partially dissociate in water
65
What is the pH range for weak acids?
pH 4-6
66
What does the symbol ⇌ indicate in a chemical equation?
The process is reversible
67
What is the difference between strong and weak acids?
Strong acids completely dissociate; weak acids do not
68
What is a concentrated solution?
One that contains a high number of acid or base molecules per dm3 of solution
69
What is a dilute solution?
One that has fewer acid or base molecules per dm3 of solution
70
What does the pH scale represent?
A logarithmic scale where each change of 1 represents a tenfold change in H+ concentration
71
What is the purpose of titrations?
To analyse the concentration of solutions
72
Why are wide range indicators not suitable for titrations?
They do not give a sharp enough colour change at the end point
73
What is the role of an indicator in a titration?
To show the endpoint of the titration
74
List some common indicators and their colours in acid.
* Litmus: Red
* Methyl orange: Red
* Phenolphthalein: Colourless
75
What is the method to perform a titration?
Add a known volume of alkali to a flask, titrate with acid until endpoint is reached
76
What should be recorded during a titration?
The volume of acid used to reach the endpoint
77
What is a mean titre?
The average volume of acid used in titrations that are concordant
78
What is the simplest ionic equation for the neutralisation reaction?
H+ + OH– ⟶ H2O
79
True or False: Anomalous results should be included in calculating the mean titre.
False
## Footnote
Only concordant results should be used.
80
Fill in the blank: The concentration of nitric acid is calculated using the formula _______.
moles/volume
## Footnote
The volume must be in dm3.
81
What is the process of electrolysis?
The breakdown of an ionic compound using an electric current.
82
What are electrolytes?
Liquids and solutions that can conduct electricity
83
Which types of compounds cannot undergo electrolysis?
Covalent compounds
84
Define anode in electrolysis
The positive electrode of an electrolysis cell
85
Define cathode in electrolysis
The negative electrode of an electrolysis cell
86
What is a cation?
A positively charged ion attracted to the cathode
87
What is an anion?
A negatively charged ion attracted to the anode
88
What mnemonic can help remember the polarity of electrodes?
PANIC: Positive (is) Anode Negative Is Cathode
89
Why can't ionic compounds in solid state conduct electricity?
Ions are fixed in lattice so cannot move and therefore cannot carry charge.
90
What happens to ions during electrolysis?
They move towards the electrodes
91
What is produced at the cathode during electrolysis of molten lead(II) bromide?
Lead metal
92
What is produced at the anode during electrolysis of molten lead(II) bromide?
Bromine gas
93
What is the extraction method for metals above carbon in the reactivity series?
Electrolysis
94
What is the extraction method for metals below carbon in the reactivity series?
Heating with carbon
95
What is the main ore of aluminium?
Bauxite
96
What is the purpose of cryolite in the electrolysis of aluminium?
It lowers the melting point of aluminium oxide
97
What common gas is produced at the anode when no halide ions are present?
Oxygen
98
What gas is produced at the cathode if the metal is above hydrogen in the reactivity series?
Hydrogen gas
99
What happens to the anode during the electrolysis?
It wears away due to reaction with oxygen, producing CO2
100
What ions are present in aqueous solutions during electrolysis?
H+ and OH– ions from water, plus ions from the compound
101
What is the discharge preference at the anode if halide ions are present?
The corresponding halogen is formed
102
What is produced at the cathode if the positive metal ion is less reactive than hydrogen?
The metal is produced
103
What is the objective of the required practical on electrolysis of aqueous solutions?
To investigate what happens during electrolysis using inert electrodes
104
Fill in the blank: The positive electrode is called the _______.
Anode
105
Fill in the blank: The negative electrode is called the _______.
Cathode
106
True or False: Electrolysis can occur in solid ionic compounds.
False
107
What happens if the electrodes are not submerged in the electrolyte?
The conductivity will fall considerably and the rate of electrolysis will be very slow.
108
What is the advantage of using graduated test tubes or measuring cylinders in electrolysis?
The volume of gas produced over time can be measured.
109
What is the first step in the electrolysis method?
Set up the apparatus as shown in the diagram.
110
Define oxidation in terms of electron transfer.
Oxidation is when a substance loses electrons.
111
Define reduction in terms of electron transfer.
Reduction is when a substance gains electrons.
112
What happens to ions at the anode during electrolysis?
Negatively charged ions lose electrons and are thus oxidised.
113
What occurs at the cathode during electrolysis?
Positively charged ions gain electrons and are thus reduced.
114
What is the half equation at the cathode for the electrolysis of molten lead(II) bromide?
Pb2+ + 2e– ⟶ Pb.
115
What is the half equation at the anode for the electrolysis of molten lead(II) bromide?
2Br- – 2e– ⟶ Br2.
116
What is the half equation at the cathode for the electrolysis of molten aluminium oxide?
Al3+ + 3e– ⟶ Al.
117
What is the half equation at the anode for the electrolysis of molten aluminium oxide?
2O2- – 4e– ⟶ O2.
118
When is hydrogen discharged at the cathode during electrolysis?
When the metal is more reactive than hydrogen.
119
When is the metal discharged at the cathode during electrolysis?
When the metal is less reactive than hydrogen.
120
What occurs at the anode if a halide ion is present?
The corresponding halogen is formed.
121
What occurs at the anode if a halide ion is not present?
Oxygen is formed as hydroxide ions are discharged.
122
What is the anode reaction for copper(II) chloride (CuCl2)?
2Cl– → Cl2 + 2e–.
123
What is the cathode reaction for copper(II) chloride (CuCl2)?
Cu2+ + 2e– → Cu.
124
What is the anode reaction for sodium chloride (NaCl)?
2Cl– → Cl2 + 2e–.
125
What is the cathode reaction for sodium chloride (NaCl)?
2H+ + 2e– → H2.
126
What is the anode reaction for copper(II) sulfate (CuSO4)?
4OH– → O2 + 2H2O + 4e–.
127
What is the cathode reaction for copper(II) sulfate (CuSO4)?
Cu2+ + 2e– → Cu.
128
What is a crucial tip for writing half equations in electrolysis?
Make sure the charges are balanced within the equation.
