ElectrolysisCambridge IGCSE Chemistry: Flashcards

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Define electrolysis.

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Define electrolysis.: Electrolysis is the decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current.
In an electrolytic cell, which electrode is positive and which is negative?: The anode is the positive electrode and the cathode is the negative electrode.
What is an electrolyte in an electrolytic cell?: The electrolyte is the molten or aqueous ionic compound being decomposed.
What type of substance is formed at the cathode during electrolysis?: Metals or hydrogen are formed at the cathode (reduction occurs here).
What type of substance is formed at the anode during electrolysis?: Non-metals (other than hydrogen) are formed at the anode (oxidation occurs here).
Name the products formed during electrolysis of molten lead(II) bromide using inert electrodes.: At the cathode: lead (Pb) as a silvery liquid. At the anode: bromine (Br₂) as a brown vapour.
Name the products formed during electrolysis of concentrated aqueous sodium chloride using inert electrodes.: At the cathode: hydrogen gas (H₂). At the anode: chlorine gas (Cl₂). Sodium hydroxide solution remains in the electrolyte.
Name the products formed during electrolysis of dilute sulfuric acid using inert electrodes.: At the cathode: hydrogen gas (H₂). At the anode: oxygen gas (O₂).
Describe how charge is transferred during electrolysis in the external circuit.: Electrons move through the external circuit from the cathode to the anode (from negative to positive electrode).
Describe the movement of ions during electrolysis in the electrolyte.: Cations (positively charged ions) move towards the cathode (negative electrode). Anions (negatively charged ions) move towards the anode (positive electrode).
Name the products formed during electrolysis of aqueous copper(II) sulfate using inert electrodes.: At the cathode: copper metal (Cu) as a red/brown deposit. At the anode: oxygen gas (O₂). The blue colour of the solution fades.
Name the products formed during electrolysis of aqueous copper(II) sulfate using copper electrodes.: At the cathode: copper metal (Cu) deposits. At the anode: copper metal dissolves. The solution remains blue.
Explain what happens during electroplating and why it is carried out.: Electroplating coats an object with a thin layer of metal by using it as the cathode in an electrolytic cell. It is done to improve appearance and increase resistance to corrosion.
Write the ionic half-equation for reduction at the cathode when Cu²⁺ ions are discharged.: Cu²⁺ + 2e⁻ → Cu
Write the ionic half-equation for oxidation at the anode when water is oxidised in dilute solution.: 4OH⁻ → O₂ + 2H₂O + 4e⁻ (or 2H₂O → O₂ + 4H⁺ + 4e⁻)