Aluminium is extracted from its ore by electrolysis.
The electrolyte is a mixture of molten aluminium oxide and cryolite.
What is the role of the cryolite?
To act as a catalyst
To lower the melting point of the aluminium oxide
To enable the aluminium oxide to conduct electricity
To lower the boiling point of aluminium oxide
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This question is about the electrolysis of zinc chloride.
Figure 1 shows the apparatus for the electrolysis of molten zinc chloride.
Figure 1
Why can electrolysis not be performed using the apparatus as shown in Figure 1?
Chloride ions move towards the positive electrode.
Explain why chloride ions move towards the positive electrode.
Name the product formed at the negative electrode.
Explain the type of reaction that occurs at the negative electrode.
Type of reaction: _______________
Explanation: __________________________________________
One of the products from the electrolysis of zinc chloride is chlorine.
Balance the half equation to show the formation of chlorine.
____ Cl– → Cl2 + ____ e–
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This question is about methods of extraction.
The method that is used to extract a metal from its ore can be determined by the position of the metal in the reactivity series.
Table 1 contains a section of the reactivity series.
Table 1
| More reactive metal / element |
| Potassium |
| Calcium |
| Aluminium |
| Carbon |
| Zinc |
| Iron |
| Copper |
| Platinum |
| Less reactive metal / element |
Draw a ring around the correct answer to complete the sentences about metal extraction.
| Displacement by carbon is used to extract |
|
|
Electrolysis is used to extract |
|
Aluminium is extracted from aluminium oxide using an electrolytic cell as shown in Figure 1.
Figure 1
Aluminium oxide consists of Al3+ ions and O2– ions.
Aluminium oxide is mixed with cryolite and melted before electrolysis takes place.
Why is the aluminium oxide mixed with cryolite?
Tick (✓) one box.
| To obtain more aluminium | |
| To increase the melting point of the mixture | |
| To decrease the melting point of the mixture | |
| To use less aluminium oxide |
What is produced at the positive electrode?
The positive carbon electrode has to be replaced periodically.
Explain why the positive electrode needs to be replaced. Your answer should include an equation.
The positive carbon electrode needs to be replaced because ____________________
Equation: ________ + ________ → ________
Complete the half equation to show the formation of aluminium.
Al3+ + _____ → Al
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This question is about electrolysis.
A student investigates the electrolysis of different salt solutions, using the equipment shown in Figure 1.
Figure 1
What observations could be made if a metal is produced at one of the electrodes?
Observation 1: ________________________________________
Observation 2: ________________________________________
Which electrode will non-metal ions such as the chloride (Cl–) and sulfate (SO42–) ion be attracted to?
An aqueous solution of copper(II) chloride is electrolysed.
Which ion is not present during this reaction?
Circle one ion.
| Cu2+ | H– | H+ | OH– | Cl– |
The student investigates the electrolysis of:
Table 1 contains a section of the reactivity series.
Table 1
| More reactive metal / element |
| Potassium |
| Sodium |
| Aluminium |
| Carbon |
| Zinc |
| Iron |
| Hydrogen |
| Copper |
| Less reactive metal / element |
Complete Table 2 to predict the products.
Choose answers from the box.
|
|
Substance electrolysed |
Product at cathode (negative electrode) |
Product at anode (positive electrode) |
|
Copper(II) chloride solution |
|
|
|
Sodium sulfate solution |
|
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This question is about the electrolysis of molten and aqueous sodium chloride.
Complete the word equation to show the products of the electrolysis of molten sodium chloride.
Sodium chloride → _______________ + _______________
The electrolysis of aqueous sodium chloride produces hydrogen gas.
Balance the half equation to show the formation of hydrogen gas.
____ H+ + ____ → H2
Chlorine is formed during the electrolysis of sodium chloride solution.
2Cl– → Cl2 + 2e–
What type of reaction is this?
Draw a ring around the correct words to complete the sentences.
| The formation of chlorine from chloride ions is |
|
reaction |
|
This reaction happens |
|
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Some metals, such as aluminium, are extracted from their ores using electrolysis.
Why are some metals extracted using electrolysis?
They are native metals
They are more reactive than carbon
They have low melting points
They conduct electricity
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This question is about electrolysis.
Draw one line from the electrolysis keyword to the correct definition.
Ionic compounds are capable of being electrolysed under certain conditions.
Complete the sentences about the electrolysis of ionic compounds.
Choose answers from the box.
|
Ionic compounds cannot conduct electricity when they are __________________.
This is because they have __________________ that can move and carry charge.
To conduct electricity, an ionic compound must be __________________ or dissolved in solution.
Draw a ring around the correct answer to complete the sentences about the movement of ions.
| Positive ions move towards the |
|
| Negative ions move towards the |
|
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Magnesium chloride is an ionic compound that can be electrolysed.
Figure 1 shows two experiments in which MgCl2 undergoes this process.
Figure 1
Explain why solid magnesium chloride cannot be electrolysed and give the necessary conditions for electrolysis to occur.
Justify the production of magnesium metal at the cathode in Experiment A.
Identify the gas produced at the cathode in Experiment B.
Explain why magnesium is not produced at the cathode in Experiment B.
Balance the half equation which occurs at the anode.
________ Cl– → Cl2 + _______
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When copper(II) sulfate undergoes electrolysis, it produces oxygen gas at the positive electrode.
The unbalanced half equation below represents the reaction that occurs at the positive electrode.
Which numbers will correctly balance the half equation?
___ OH- → O2 + ___ H2O + ___ e-
2,2,2
2,4,2
4,2,4
4,4,2
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This question is about the extraction of aluminium using electrolysis. The process is displayed in Figure 3.
Figure 3
Why isn’t aluminum extracted by heating with carbon?
Explain why aluminium is formed at the cathode.
Explain why carbon dioxide is formed at the anode and why the anode must be continually replaced.
The electrolyte in the process consists of a mixture of aluminium oxide and cryolite.
Explain why a mixture is used instead of just the aluminium oxide.
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This question is about the electrolysis of sulfuric acid. The apparatus used in this process is shown in Figure 4.
Oxygen is formed at the anode.
Figure 4
Solutions which decompose when electricity is passed through them have a specific name.
What is the name given to these solutions?
The half equation for the reaction which occurs at the anode is:
4OH– → 2H2O + O2 + 4e–
Describe what type of reaction this is and give a reason for your answer.
Write a balanced half equation for the reaction which occurs at the cathode.
As the electricity is passed through the electrolyte what happens to the concentration of the sulfuric acid?
Explain your answer.
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A student electrolysed a solution of potassium chloride with the intention of isolating potassium.
The apparatus was set up as shown in Figure 5.
Figure 5
The student expected to see potassium metal being formed at the cathode but instead observed bubbles of gas being formed.
Name the gas produced at the cathode and explain why this gas is produced, giving a reason why potassium is not produced.
The student then electrolysed molten potassium chloride instead of a solution and found that potassium metal was produced at the negative electrode.
Describe how potassium atoms are produced from ions of potassium.
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During the the electrolysis of copper sulfate solution, copper ions move to the negative electrode.
What is the reason for this?
Copper is less reactive than hydrogen and consists of negatively charged ions
Copper is more reactive than hydrogen and consists of negatively charged ions
Copper is less reactive than hydrogen and consists of positively charged ions
Copper is more reactive than hydrogen and consists of positively charged ions
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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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Hydrogen, chlorine and sodium hydroxide are commercially important chemicals which can all be made in one process.
The process involves passing electricity through an aqueous solution of sodium chloride (brine).
Figure 2 shows an electrolytic cell in which this process can be carried out.
Figure 2
Identify the substances produced at points A, B and C.
A _________________________
B _________________________
C _________________________
Complete and balance the equations for the reactions at the electrodes.
___Cl– – ___e– → Cl2
___H + ___e– → H2
Identify the compound in the cell responsible for producing the hydrogen ions.
What kind of particles must be able to pass through the barrier so that electrolysis can take place?
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This question is about electrolysis.
A student investigated the electrolysis of copper chromate solution.
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, are yellow.
Explain the colour of copper chromate solution.
The student's apparatus to electrolyse copper chromate solution using zinc electrodes is shown in Figure 1.
Explain why the negative electrode increases in mass.
The student replaces the zinc electrodes with carbon electrodes.
Explain why the mass of one of the electrodes decreases.
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This question is about the electrolysis of aluminium oxide.
Explain why aluminium is extracted from its ore by electrolysis.
Explain why cryolite is used in the extraction of aluminium.
Aluminium oxide undergoes a redox reaction during electrolysis.
Explain whether aluminium is produced as the result of a reduction or an oxidation reaction.
Your answer should include an appropriate equation including state symbols.
Explain what happens to the anode during the electrolysis of aluminium oxide.
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This question is about the electrolysis of zinc(II) chloride, ZnCl2.
Zinc(II) chloride can conduct electricity when it is molten or dissolved in solution.
Explain why zinc(II) chloride cannot conduct electricity when it is solid.
In terms of structure and bonding, explain why graphite is commonly used as the electrode in electrolysis reactions.
Explain how the product at each electrode is formed during the electrolysis of molten zinc chloride.
The electrolysis of molten zinc chloride gives different products compared to the electrolysis of aqueous zinc chloride.
Explain any differences in the products from each electrolysis experiment.
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Sodium chloride solution can undergo electrolysis.
What product will be formed at the negative electrode?
Oxygen
Chlorine
Hydrogen
Sodium
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This question is about the electrolysis of sulfuric acid.
A student investigated how the volume of gases produced changes with time in the electrolysis of dilute sulfuric acid.
The apparatus is shown in Figure 1.
Figure 1
The student has made an error in the apparatus.
Explain how the apparatus should be changed.
With the help of suitable equations, explain why it is more likely that the hydrogen formed in this electrolysis comes from the sulfuric acid than water.
Sulfate ions and hydroxide ions are both attracted to the anode.
Hydroxide ions are less stable than sulfate ions so they are discharged at the anode.
OH– (aq) → OH (aq) + e–
The OH groups produced exist for a fraction of a second before they form water and oxygen.
Write a balanced symbol equation, including state symbols, for this reaction.
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Electrolysis can be used to separate molten lead bromide.
Which statement is true for what happens at the negative electrode?
Lead atoms are oxidised
Lead atoms are reduced
Lead ions are oxidised
Lead ions are reduced
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This question is about sodium chloride.
Describe, in terms of electrons and with the help of suitable equations, what happens during the electrolysis of molten sodium chloride.
The products of electrolysis of molten sodium chloride are different to those of aqueous sodium chloride.
Explain the different products from the electrolysis of aqueous sodium chloride.
Nuclear submarines can stay underwater for months without needing to come to the surface.
Oxygen for the crew to breathe is produced using a piece of equipment called an automated electrolytic oxygen generator.
Many people assume that seawater is electrolysed to produce the oxygen, this assumption is incorrect.
Explain why the assumption is not only incorrect but potentially hazardous and how the oxygen can be produced by electrolysis.
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