Electrolysis Revision - AQA Chemistry 8462

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42 objective pages available

The process of electrolysis9 objectives

Define electrolysis as the splitting up of an ionic compound using electricity.
Describe an electrolyte as a liquid that contains free-moving ions.
Explain why ionic compounds must be molten or dissolved in water for electrolysis to occur.
Identify the positive electrode as the anode.
Identify the negative electrode as the cathode.
Describe movement of positive ions to the cathode during electrolysis.
Describe movement of negative ions to the anode during electrolysis.
Explain why ions are discharged at electrodes during electrolysis.
Link electrolysis to decomposition of ionic compounds.

Electrolysis of molten ionic compounds7 objectives

Explain why molten ionic compounds conduct electricity.
Predict that a metal forms at the cathode when a molten ionic compound is electrolysed.
Predict that a non-metal forms at the anode when a molten ionic compound is electrolysed.
Describe electrolysis of molten lead bromide as producing lead at the cathode and bromine at the anode.
Write word equations for electrolysis of molten ionic compounds.
Write balanced symbol equations for electrolysis of molten ionic compounds when formulae are supplied.
Explain electrode products using movement and discharge of ions.

Using electrolysis to extract metals8 objectives

Explain why aluminium is extracted by electrolysis rather than reduction with carbon.
Describe aluminium oxide as the aluminium compound used in extraction.
Explain why aluminium oxide is dissolved in molten cryolite during extraction.
Describe aluminium ions gaining electrons at the cathode to form aluminium.
Describe oxide ions losing electrons at the anode to form oxygen.
Explain why carbon anodes are gradually used up during aluminium extraction.
Write word equations for the main reactions in aluminium extraction.
(HT only) Write half equations for aluminium ion reduction and oxide ion oxidation when formulae and charges are supplied.

Electrolysis of aqueous solutions10 objectives

Describe that aqueous solutions contain ions from the ionic compound and hydrogen ions and hydroxide ions from water.
Predict that hydrogen is produced at the cathode if the metal is more reactive than hydrogen.
Predict that the metal is produced at the cathode if it is less reactive than hydrogen.
Predict that oxygen is produced at the anode unless the solution contains halide ions.
Predict that chlorine, bromine or iodine is produced at the anode when the corresponding halide ion is present.
Explain products of aqueous electrolysis using the reactivity series and ions present.
Describe how to investigate electrolysis of aqueous solutions using inert electrodes. (AT 3, AT 7)
Make and test predictions about products formed during electrolysis of aqueous solutions. (WS 2.2)
Identify products of aqueous electrolysis using suitable chemical tests where appropriate.
Compare products from electrolysis of molten and aqueous ionic compounds.

Representation of reactions at electrodes as half equations (HT only)8 objectives

(HT only) Write half equations for reactions at the cathode in electrolysis.
(HT only) Write half equations for reactions at the anode in electrolysis.
(HT only) Explain that reduction happens at the cathode because positive ions gain electrons.
(HT only) Explain that oxidation happens at the anode because negative ions lose electrons.
(HT only) Balance charge and atoms in simple electrolysis half equations.
(HT only) Interpret half equations to identify products formed at electrodes.
(HT only) Distinguish cathode half equations from anode half equations.
(HT only) Link half equations to observed products in molten and aqueous electrolysis.

ElectrolysisIonic Compoundelectrolytefree‑moving ionsElectrolyteanodeelectrodecathodepositive ionsnegative ionsElectrodeDecomposition

Understand Electrolysis Basics: Link the chemical change carefully by remember that electrolysis involves the splitting of ionic compounds using electricity, which requires free-moving ions. Link your answer to The process of electrolysis in Electrolysis, and name the acid-base term, ion, electrode, reaction type, product, observation, or salt-preparation step where relevant.
Understand Electrolytes: Link the chemical change carefully by remember that an electrolyte is a liquid containing free-moving ions, which is essential for electrolysis to occur. Link your answer to The process of electrolysis in Electrolysis, and name the acid-base term, ion, electrode, reaction type, product, observation, or salt-preparation step where relevant.

Misunderstanding Electrolysis Definition: Emphasize that electrolysis specifically refers to the process of breaking down ionic compounds into their constituent ions using electricity.
Misunderstanding Electrolytes: Emphasize that an electrolyte specifically refers to a liquid that contains ions, which are necessary for conducting electricity.

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