Exam code: 0620 & 0971
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A student was investigating the electrolysis of zinc chloride.
What is the correct reason for electrolysis not working?
Solid zinc chloride has been used
The electrodes don't conduct electricity
The power supply is not connected properly
The crucible is too small to allow ions to flow
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Solid lead(II) bromide is heated until it is molten. The molten lead (II) bromide then undergoes electrolysis.
Which substances are formed at each electrode?
| anode | cathode |
A | bromine | lead |
B | lead | bromine |
C | bromine | hydrogen |
D | hydrogen | lead |
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The electrolysis of concentrated hydrochloric acid is shown.
Which statement describes what happens to the electrons during the electrolysis?
They are removed from hydrogen ions at the negative electrode
They are added to hydrogen ions at the negative electrode
They are added to chloride ions at the positive electrode
They move through the electrolyte solution to the positive electrode
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Concentrated aqueous sodium chloride can be electrolysed.
Which statement is correct?
Hydrogen gas is formed at the anode, and chlorine gas is formed at the cathode.
Hydrogen gas is formed at the cathode, and chlorine gas is formed at the anode.
Sodium metal is formed at the anode, and chlorine gas is formed at the cathode.
Sodium metal is formed at the cathode, and chlorine gas is formed at the anode.
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The diagram shows the electrolysis of concentrated hydrochloric acid and concentrated aqueous sodium chloride using carbon electrodes.
At which electrode(s) is hydrogen produced?
Electrode 1 only
Electrodes 1 and 3
Electrode 2 only
Electrodes 2 and 4
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Three statements about the electrolysis of molten lead (II) bromide are listed.
A green gas is produced at the negative electrode.
Lead ions will gain electrons at the cathode.
The electrodes for the electrolysis must be from an inert material, such as graphite.
Which statements are correct?
1, 2 and 3
2 only
2 and 3 only
3 only
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Which statement about electrolysis is correct?
Electrons move through the electrolyte from the cathode to the anode.
Electrons move towards the cathode in the external circuit.
Negative ions move towards the anode in the external circuit.
Positive ions move through the electrolyte towards the anode during electrolysis.
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Dilute sulfuric acid is electrolysed using inert electrodes.
What are the products of this electrolysis?
| cathode | anode |
A | oxygen | sulfur |
B | hydrogen | sulfur dioxide |
C | oxygen | hydrogen |
D | hydrogen | oxygen |
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Electricity is passed through concentrated aqueous sodium chloride. Inert electrodes are used.
Which products are formed at the electrodes?
| cathode | anode |
A | hydrogen | chlorine |
B | hydrogen | oxygen |
C | sodium | chlorine |
D | sodium | oxygen |
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The diagram shows the electrolysis of aqueous copper(II) sulfate.
Which statement is correct?
Copper metal is deposited at the positive electrode.
In the external circuit the electrons move from positive to negative.
In the solution the electrons move from positive to negative.
Oxygen gas is produced at the positive electrode.
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Concentrated aqueous potassium bromide solution is electrolysed using inert electrodes. The ions present in the solution are K+, Br–, H+ and OH–.
To which electrodes are the ions attracted during this electrolysis?
| attracted to anode | attracted to cathode |
A | Br– and K+ | H+ and OH– |
B | Br– and OH– | H+ and K+ |
C | H+ and K+ | Br– and OH– |
D | H+ and OH– | Br– and K+ |
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Which is the correct equation for the formation of chlorine gas at the anode during the electrolysis of concentrated sodium chloride solution?
Cl + e- → Cl-
2Cl- + 2e- → Cl2
2Cl- → Cl2 + 2e-
Cl- → Cl + e-
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Concentrated aqueous magnesium chloride is electrolysed using inert graphite electrodes.
Which row shows the correct observations at the cathode and at the anode?
observation at the cathode | observation at the anode | |
A | bubbles of a colourless gas | bubbles of a colourless gas |
B | bubbles of a colourless gas | bubbles of a pale yellow-green gas |
C | silvery solid deposited | bubbles of a colourless gas |
D | silvery solid deposited | bubbles of a pale yellow-green gas |
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The diagram shows the electrolysis of concentrated aqueous sodium chloride.
What is the colour of the litmus at each electrode after five minutes?
| colour at anode | colour at cathode |
A | blue | red |
B | red | blue |
C | red | colourless |
D | colourless | blue |
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Four substances are electrolysed. The substances are concentrated aqueous sodium chloride, concentrated hydrochloric acid, molten lead(II) bromide and molten sodium oxide.
Which statement about these electrolysis reactions is correct?
A colourless gas is formed at the anode when molten sodium oxide is electrolysed.
A green gas is formed at the cathode when concentrated hydrochloric acid is electrolysed.
A metal is formed at the anode when molten lead(II) bromide is electrolysed.
A metal is formed at the cathode when concentrated aqueous sodium chloride is electrolysed.
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Four solutions are separately electrolysed.
experiment | solution | electrodes |
1 | dilute aqueous sodium chloride | carbon |
2 | aqueous copper(II) sulfate | copper |
3 | concentrated hydrochloric acid | carbon |
4 | dilute sulfuric acid | carbon |
In which two experiments is a colourless gas evolved at the anode?
1 & 2
1 & 4
2 & 3
3 & 4
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During electrolysis of brine, a gas is produced at the cathode. What is the half-equation for the reaction on the cathode?
2Cl- → Cl2 + 2e-
2Cl- + 2e- → Cl2
2H+ + 2e- → H2
2H+ → H2 + 2e-
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The amount of gases P and Q are formed when substance X is electrolysed.
What is substance X?
molten zinc bromide
dilute sulfuric acid
concentrated aqueous sodium bromide
concentrated hydrochloric acid
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Concentrated aqueous sodium chloride, dilute sulfuric acid and molten lead bromide were electrolysed separately in experiments 1, 2 and 3.
Which statement about the electrode products is correct?
Metals were formed at the anode in experiments 1 and 3 only
Metals were formed at the cathode in experiments 1 and 3 only
Gases are given off at the cathode in experiments 1 and 2 only
Gases are given off at the anode in experiments 2 and 3 only
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A student wants to identify the gas produced at the negative electrode during the electrolysis of aqueous sodium chloride.
What is the correct test for the gas produced?
A glowing splint will relight
A burning splint gives a squeaky pop sound
Damp litmus paper bleaches
Damp red litmus paper turns blue
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