Chemical Changes Flashcards
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
Provide an example of a displacement reaction.
Mg + CuSO4 → MgSO4 + Cu.
27
What happens when a substance gains electrons?
It is reduced
## Footnote
This is a key concept in redox reactions.
28
What type of reaction occurs when iron reacts with copper sulfate?
Displacement reaction
## Footnote
This reaction can be represented as: Fe + CuSO4 → FeSO4 + Cu.
29
What is the ionic equation for the reaction between iron and copper sulfate?
Fe + Cu2+ + SO42– → Fe2+ + SO42– + Cu
## Footnote
The sulfate ions are spectator ions.
30
What are spectator ions?
Ions that appear unchanged on both sides of a reaction
## Footnote
In the ionic equation, SO42– is a spectator ion.
31
How can the ionic equation be simplified by removing spectator ions?
Fe + Cu2+ → Fe2+ + Cu
## Footnote
This represents the net ionic equation.
32
What does the half-equation Fe → Fe2+ + 2e– illustrate?
Oxidation
## Footnote
Iron loses electrons to become a positive ion.
33
What does the half-equation Cu2+ + 2e– → Cu illustrate?
Reduction
## Footnote
Copper gains electrons to become a neutral atom.
34
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.
35
In the reaction V3+ + Fe3+ → V4+ + Fe2+, which species is oxidised?
V3+
## Footnote
V3+ loses an electron to become V4+.
36
In the same reaction, which species is reduced?
Fe3+
## Footnote
Fe3+ gains an electron to become Fe2+.
37
What is the full equation for the displacement of copper by zinc?
Zn (s) + CuSO4 (aq) → ZnSO4 (aq) + Cu (s)
## Footnote
This shows the displacement reaction between zinc and copper sulfate.
38
What is the ionic equation for the displacement of copper by zinc?
Zn (s) + Cu2+ (aq) + SO42– (aq) → Zn2+ (aq) + SO42– (aq) + Cu (s)
## Footnote
Spectator ions can be ignored in this equation.
39
What species undergoes oxidation in the ionic equation Zn (s) + Cu2+ (aq) → Zn2+ (aq) + Cu (s)?
Zn (s)
## Footnote
Zinc is oxidised to Zn2+ by losing electrons.
40
What species undergoes reduction in the same ionic equation?
Cu2+ (aq)
## Footnote
Copper is reduced to Cu by gaining electrons.
41
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.
42
What is the general equation for the reaction of a metal with an acid?
metal + acid ⟶ salt + hydrogen
43
Which metals can react with dilute acids?
Only metals above hydrogen in the reactivity series
44
What type of salts do sulfuric acid and hydrochloric acid produce when reacting with metals?
* Sulfuric acid: sulfate salts
* Hydrochloric acid: chloride salts
45
What is a redox reaction?
A reaction involving both reduction and oxidation occurring simultaneously
46
What happens to zinc in the reaction with hydrochloric acid?
Zinc is oxidised as it loses electrons
47
In metal-acid reactions, what happens to hydrogen ions?
Hydrogen ions are reduced as they gain electrons
48
What is produced in an acid-base neutralisation reaction?
Salt and water
49
What do you call a base that dissolves in water?
Alkali
50
What is the result when a metal carbonate reacts with an acid?
Salt, water, and carbon dioxide
51
What indicates the presence of carbon dioxide gas in a reaction?
The limewater turns milky or cloudy
52
What ions does hydrochloric acid produce in salts?
Chloride ions (Cl–)
53
How are the names of salts derived?
The first part comes from the metal/base, and the second part comes from the acid
54
What is the formula for magnesium phosphate?
Mg3(PO4)2
55
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
56
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
57
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
58
What do acids produce when dissolved in water?
Positively charged hydrogen ions (H+)
59
What pH values do bases have?
pH values above 7
60
What is the outcome of an acid reacting with a metal oxide?
Metal salt and water
61
What is the effect of adding acids to water?
They form positively charged hydrogen ions (H+)
62
What is the effect of adding alkalis to water?
They form negative hydroxide ions (OH–)
63
What does the pH scale measure?
The amount of hydrogen ions present in a solution
64
What is the pH range for acids?
Below 7
65
What is the pH range for alkalis?
Above 7
66
What pH value is considered neutral?
7
67
What pH range indicates a strong acid?
pH 1-3
68
What pH range indicates a weak acid?
pH 4-6
69
What pH range indicates a weak alkali?
pH 8-11
70
What pH range indicates a strong alkali?
pH 12-14
71
How can pH be measured?
Using a digital pH meter or an indicator
72
What is a universal indicator?
A wide range indicator that gives an approximate pH value
73
What does a neutralisation reaction involve?
An acid reacting with an alkali to produce water
74
What is the net ionic equation for neutralisation?
H+ (aq) + OH– (aq) → H2O (l)
75
What do strong acids do in water?
Dissociate completely to produce a high concentration of H+ ions
76
Give examples of strong acids.
* Hydrochloric acid (HCl)
* Nitric acid (HNO3)
* Sulfuric acid (H2SO4)
77
What characterizes weak acids?
They partially dissociate in water
78
What is the pH range for weak acids?
pH 4-6
79
What does the symbol ⇌ indicate in a chemical equation?
The process is reversible
80
What is the difference between strong and weak acids?
Strong acids completely dissociate; weak acids do not
81
What is a concentrated solution?
One that contains a high number of acid or base molecules per dm3 of solution
82
What is a dilute solution?
One that has fewer acid or base molecules per dm3 of solution
83
What does the pH scale represent?
A logarithmic scale where each change of 1 represents a tenfold change in H+ concentration
84
What is the purpose of titrations?
To analyse the concentration of solutions
85
Why are wide range indicators not suitable for titrations?
They do not give a sharp enough colour change at the end point
86
What is the role of an indicator in a titration?
To show the endpoint of the titration
87
List some common indicators and their colours in acid.
* Litmus: Red
* Methyl orange: Red
* Phenolphthalein: Colourless
88
What is the method to perform a titration?
Add a known volume of alkali to a flask, titrate with acid until endpoint is reached
89
What should be recorded during a titration?
The volume of acid used to reach the endpoint
90
What is a mean titre?
The average volume of acid used in titrations that are concordant
91
What is the balanced symbol equation for the reaction between copper(II) hydroxide and sulfuric acid?
Cu(OH)2 + H2SO4 ⟶ CuSO4 + 2H2O
92
What is the simplest ionic equation for the neutralisation reaction?
H+ + OH– ⟶ H2O
93
What should be used to calculate a mean titre?
Only concordant results
## Footnote
Concordant results are those that are in agreement with each other and show minimal variation.
94
What is the purpose of calculating the mean titre?
To calculate the concentration of the acid in mol/dm3, ignoring any anomalous results
## Footnote
Anomalous results are those that differ significantly from other results.
95
What is the first step in titration calculations?
Calculate the number of moles of barium hydroxide
## Footnote
This involves using the formula: Moles = concentration x volume.
96
What is the formula to calculate moles of a substance?
Moles = concentration x volume (dm3)
## Footnote
Volume must be in dm3 for the calculation.
97
How many moles of barium hydroxide are in 25.00 cm3 of 0.15 mol/dm3?
3.75 x 10–3 mols
## Footnote
This is calculated as 0.15 x 0.025.
98
How do you calculate moles of nitric acid from barium hydroxide?
Multiply the moles of barium hydroxide by 2
## Footnote
This is due to the 1:2 ratio in the neutralization reaction.
99
What is the moles of nitric acid when 3.75 x 10–3 moles of barium hydroxide are used?
7.5 x 10–3 moles
## Footnote
This is derived from 3.75 x 10–3 x 2.
100
What is the final step in calculating the concentration of nitric acid?
Divide moles of nitric acid by the volume of nitric acid in dm3
## Footnote
Remember to convert cm3 to dm3 by dividing by 1000.
101
What is the concentration of nitric acid calculated from 7.5 x 10–3 moles in 12.80 cm3?
0.59 mol/dm3
## Footnote
This is rounded to 2 decimal places.
102
True or False: Anomalous results should be included in calculating the mean titre.
False
## Footnote
Only concordant results should be used.
103
Fill in the blank: The concentration of nitric acid is calculated using the formula _______.
moles/volume
## Footnote
The volume must be in dm3.
104
What is the process of electrolysis?
The decomposition of a compound when an electric current is passed through it
105
What are electrolytes?
Liquids and solutions that can conduct electricity
106
Which types of compounds cannot undergo electrolysis?
Covalent compounds
107
What is an electrolytic cell?
The set-up used in electrolysis consisting of electrodes and an electrolyte
108
Define anode in electrolysis
The positive electrode of an electrolysis cell
109
Define cathode in electrolysis
The negative electrode of an electrolysis cell
110
What is a cation?
A positively charged ion attracted to the cathode
111
What is an anion?
A negatively charged ion attracted to the anode
112
What mnemonic can help remember the polarity of electrodes?
PANIC: Positive (is) Anode Negative Is Cathode
113
Why can't ionic compounds in solid state conduct electricity?
They have no free ions that can move and carry charge
114
What happens to ions during electrolysis?
They move towards the electrodes
115
What is produced at the cathode during electrolysis of molten lead(II) bromide?
Lead metal
116
What is produced at the anode during electrolysis of molten lead(II) bromide?
Bromine gas
117
What is the extraction method for metals above carbon in the reactivity series?
Electrolysis
118
What is the extraction method for metals below carbon in the reactivity series?
Heating with carbon
119
What is the main ore of aluminium?
Bauxite
120
What is the purpose of cryolite in the electrolysis of aluminium?
It lowers the melting point of aluminium oxide
121
What common gas is produced at the anode when no halide ions are present?
Oxygen
122
What gas is produced at the cathode if the metal is above hydrogen in the reactivity series?
Hydrogen gas
123
What happens to the anode during the electrolysis of aluminium?
It wears away due to reaction with oxygen, producing CO2
124
What ions are present in aqueous solutions during electrolysis?
H+ and OH– ions from water, plus ions from the compound
125
What is the discharge preference at the anode if halide ions are present?
The corresponding halogen is formed
126
What is produced at the cathode if the positive metal ion is less reactive than hydrogen?
The metal is produced
127
How can you identify hydrogen gas produced at the cathode?
It burns with a ‘pop’ with a lighted splint
128
How can you identify oxygen gas produced at the anode?
It relights a glowing splint dipped into the gas
129
What is the objective of the required practical on electrolysis of aqueous solutions?
To investigate what happens during electrolysis using inert electrodes
130
Fill in the blank: The positive electrode is called the _______.
Anode
131
Fill in the blank: The negative electrode is called the _______.
Cathode
132
True or False: Electrolysis can occur in solid ionic compounds.
False
133
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.
134
What is the advantage of using graduated test tubes or measuring cylinders in electrolysis?
The volume of gas produced over time can be measured.
135
What is the first step in the electrolysis method?
Set up the apparatus as shown in the diagram.
136
What type of solutions are suitable for the electrolysis investigation?
* Copper chloride
* Copper sulfate
* Sodium chloride
* Sodium bromide
* Sodium nitrate
137
What is the observation at the anode when using aqueous sodium nitrate?
Effervescence, no colour, splint relights so gas is oxygen.
138
What is the observation at the cathode when using aqueous sodium nitrate?
Effervescence, no colour, squeaky pop, so gas is hydrogen.
139
What is the test result for hydrogen gas?
Lighted splint goes out with a squeaky pop.
140
What is the test result for oxygen gas?
A glowing splint relights.
141
What happens to damp blue litmus paper in the presence of chlorine?
Turns red and is then bleached white.
142
Define oxidation in terms of electron transfer.
Oxidation is when a substance loses electrons.
143
Define reduction in terms of electron transfer.
Reduction is when a substance gains electrons.
144
What occurs at the anode during electrolysis?
Negatively charged ions lose electrons and are thus oxidised.
145
What occurs at the cathode during electrolysis?
Positively charged ions gain electrons and are thus reduced.
146
What is the half equation at the cathode for the electrolysis of molten lead(II) bromide?
Pb2+ + 2e– ⟶ Pb.
147
What is the half equation at the anode for the electrolysis of molten lead(II) bromide?
2Br- – 2e– ⟶ Br2.
148
What is the half equation at the cathode for the electrolysis of molten aluminium oxide?
Al3+ + 3e– ⟶ Al.
149
What is the half equation at the anode for the electrolysis of molten aluminium oxide?
2O2- – 4e– ⟶ O2.
150
When is hydrogen discharged at the cathode during electrolysis?
When the metal is more reactive than hydrogen.
151
When is the metal discharged at the cathode during electrolysis?
When the metal is less reactive than hydrogen.
152
What occurs at the anode if a halide ion is present?
The corresponding halogen is formed.
153
What occurs at the anode if a halide ion is not present?
Oxygen is formed as hydroxide ions are discharged.
154
What is the anode reaction for copper(II) chloride (CuCl2)?
2Cl– → Cl2 + 2e–.
155
What is the cathode reaction for copper(II) chloride (CuCl2)?
Cu2+ + 2e– → Cu.
156
What is the anode reaction for sodium chloride (NaCl)?
2Cl– → Cl2 + 2e–.
157
What is the cathode reaction for sodium chloride (NaCl)?
2H+ + 2e– → H2.
158
What is the anode reaction for copper(II) sulfate (CuSO4)?
4OH– → O2 + 2H2O + 4e–.
159
What is the cathode reaction for copper(II) sulfate (CuSO4)?
Cu2+ + 2e– → Cu.
160
What is a crucial tip for writing half equations in electrolysis?
Make sure the charges are balanced within the equation.
