Unit 1 Basic Principles of Chemistry Chp 10: Electrolysis

What is electrolysis? 

A chemical change caused by passing an electric current through a compound which is either molten or aqueous (solution)

OBJR

What is electrode and define anode and cathode?

Electrode: Substance that can conduct electricity. 

Anode: Electrode which is connected with positive terminal of battery or power supply. 

Cathode: Electrode which is connected with negative terminal of battery or power supply.

What is electrolyte?

Liquid or solution that undergoes electrolysis.

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What ions are attracted to which electrode anf gain/lose electrons to form atom?

Positive ions (cations) are attracted to negative electrode (cathode). They gain electrons to form atoms. 

Negative ions (anions) are attracted to positive electrode (anode). They lose electrons to form atoms.

What are the properties of an electrode

High melting point. 

Conduct electricity. 

Do not dissolve in the electrolyte.

FAQ

What materials are mostly used for metal and non-metal electrodes?

Metal electrode: platinum 

Non-metal electrode: carbon (graphite)

Why bulb in external circuit wouldn’t light up?

Without ion→no ion movement in electrolyte→the bulb in the circuit doesn’t light up.

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What is oxidation, reduction and a redox reaction?

Oxidation: when something loses electrons (at the anode because negative ions lose electrons to form atoms)

Reduction: when something gains electrons. 

(at the cathode because positive ions gain electrons to form atoms) 

Redox reaction: Oxidation and reduction take place together

OBJQ + FAQ

Explain the electrolysis of molten lead(II) bromide: which component of the compound went to which electrode, which process ions undergo, equation and observation at anode.

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Explain the electrolysis of molten aluminium oxide: which component of the compound went to which electrode, which process ions undergo, equation and observation at anode.

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Explain the electrolysis of molten zinc chloride in terms of where reduction and oxidation happen (equation), products and observations at the anode.

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Explain the electrolysis of an aqueous solution in concentrated sodium chloride solution in terms of which positive and negative ions move to which electrode, the reaction at the cathode and anode and the observations at each electrode, with products

FAQ

Describe the order of elements in the reactivity series and explain 4 rules

If the metal is high in the reactivity series→hydrogen produced at the cathode instead of the metal

If the metal is below hydrogen in the reactivity series→metal is obtained at the cathode 

Dissolve in solution of halide (chloride, fluoride, bromide and iodide) → obtain halogen (chlorine, fluorine, bromine, iodine) at anode 

Dissolve in common negative ions (sulfate, nitrate, hydroxide) → obtain oxygen at the anode

OBJQ + FAQ

Explain the electrolysis of an aqueous solution in copper (II) sulfate using inert electrodes in terms of which positive and negative ions move to which electrode, the reaction at the cathode and anode and the observations at each electrode, with products and overall colour change