1.55C: Understand Why Covalent Compounds Do Not Conduct Electricity

COVALENT COMPOUND: Compound with bonds between Non-Metal and Non-Metal formed by shared pair of electrons between the two atoms

ELECTRICAL CONDUCTIVITY OF COVALENT COMPOUNDS:

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• Covalent compounds do not conduct electricity as all valence electrons are used in forming covalent bonds, therefore there are no delocalised electrons that are free to move to conduct an electric charge

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Example: Water ( H2O )

Water does not conduct electricity as all valence electrons are used in forming covalent bonds, so there are no delocalised electrons that are free to move to conduct an electric charge

1.56C: Understand Why Ionic Compounds Conduct Electricity Only When Molten or In Aqueous Solution

IONIC COMPOUNDS: Formed when atoms of Metals transfer electrons to atoms of Non-Metals to form compounds made up of ions

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                                    Diagram showing Particles of Ionic Compounds in solids

                                     and when Molten or in Solution Form

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ELECTRICAL CONDUCTIVITY OF IONIC COMPOUNDS:

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• Ionic compounds cannot conduct electricity when in solid state as ions are fixed in structure and are not free to move
• However, ionic compounds can conduct electricity when molten or in aqueous solution as their ions are free to move to conduct an electric charge

1.57C: Know that Anion and Cation are Terms Used to Refer to Negative and Positive Ions Respectively

*ANION: Negative ions (Non-Metals) that are attracted to the positive electrode

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REACTION AT THE POSITIVE ELECTRODE (ANODE)

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• Anions (Negative Non-Metal ions) are attracted to the positive electrode
• When they get to the electrode, they lose Electrons to form atoms

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Example: When Lead (II) Bromide is electrolysed, Bromide ion loses an electron to form Bromine atoms:

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2Br -     -     2e-     →     Br2

*Bromine is Formed at the Positive Electrode

*CATION: Positive ions (Metals) that are attracted to the negative electrode

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REACTION AT THE NEGATIVE ELECTRODE (CATHODE)

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• Cations (Positive Metal ions) are attracted to the negative electrode
• When they get to the electrode, they gain electrons to form Atoms

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Example: When Lead (II) Bromide is electrolysed, Lead (II) Ions gain electrons to form Lead atoms:

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Pb2+     +     2e-     →     Pb

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*Lead is Formed at the Negative Electrode

1.58C: Describe Experiments to Investigate Electrolysis, Using Inert Electrode, of Molten Compounds (Including Lead (II) Bromide) and Aqueous Solutions (Including Sodium, Chloride, Dilute Sulfuric Acid and Copper (II) Sulphate) and to Predict the Products

ELECTROLYSIS: Decomposition of an ionic substance by passing an electric current through it

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ELECTROLYSIS OF LEAD (II) BROMIDE:

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ELECTROLYSIS OF LEAD (II) BROMIDE
Diagram showing the Electrolysis of Lead (II) Bromide
METHOD: Add Lead (II) Bromide into a beaker and heat until molten, allowing ions to be free to move to conduct an electric charge Add two Graphite rods as the electrodes and connect this to a power pack or battery Turn on power pack or battery and allow Electrolysis to occur
REACTION AT ELECTRODES:
SOLUTION	PRODUCT AT POSITIVE ELECTRODE	PRODUCT AT NEGATIVE ELECTRODE
LEAD (II) BROMIDE ( PbBr2 )	Bromine   -   Br2 2Br -     -     2e-     →     Br2	Lead   -   Pb Pb2+     +     2e-     →     Pb

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ELECTROLYSIS OF AQUEOUS SOLUTIONS:

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RULES:

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• Aqueous Solutions will Always have Water ( H2O )

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Positive Electrode

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• Either Oxygen or Non-Metal will be produced E.g Chlorine, Bromine, Nitrogen

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Negative Electrode

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• Either Hydrogen or Metal will be produced
• If Metal is above Hydrogen in Reactivity Series, Hydrogen will be produced
• If Metal is below Hydrogen in Reactivity Series, Metal will be produced

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ELECTROLYSIS OF AQUEOUS SOLUTIONS
Diagram showing the Electrolysis of Aqueous Solutions
METHOD: Add Aqueous Solution into a beaker Add two Graphite rods as the electrodes and connect this to a power pack or battery Turn on power pack or battery and allow Electrolysis to occur
REACTION AT ELECTRODES:
AQUEOUS SOLUTION	PRODUCT AT POSITIVE ELECTRODE	PRODUCT AT NEGATIVE ELECTRODE
SODIUM CHLORIDE ( NaCl )	Chlorine   -   Cl 2Cl-  -  2e-  →  Cl2	Hydrogen    -   H2 2H2O  +  2e-  →  H2  +  2OH-
DILUTE SULFURIC ACID ( H2SO4 )	Oxygen   -   O2 2H2O  -  4e-  →  O2  +  4H+	Hydrogen   -    H2 2H+  +  2e-  →  H2
COPPER (II) SULFATE ( CuSO4 )	Oxygen   -   O2 2H2O  -  4e-  →  O2  +  4H+	Copper   -   Cu Cu2+  +  2e-  →  Cu

1.59C: Write Ionic Half - Equations Representing the Reactions at the Electrodes during Electrolysis and Understand Why These Reactions are Classified as Oxidation or Reduction

ELECTROLYSIS: Decomposition of an ionic substance by passing an electric current through it

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REACTION AT ELECTRODES:

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SOLUTION	PRODUCT AT POSITIVE ELECTRODE	PRODUCT AT NEGATIVE ELECTRODE
LEAD (II) BROMIDE ( PbBr2 )	Bromine   -   Br2 2Br -     -     2e-     →     Br2	Lead   -   Pb Pb2+     +     2e-     →     Pb
SODIUM CHLORIDE ( NaCl )	Chlorine - Cl 2Cl-  -  2e-  →  Cl2	Hydrogen - H2 2H2O  +  2e-  →  H2  +  2OH-
DILUTE SULFURIC ACID ( H2SO4 )	Oxygen - O2 2H2O  -  4e-  →  O2  +  4H+	Hydrogen - H2 2H+  +  2e-  →  H2
COPPER (II) SULFATE ( CuSO4 )	Oxygen - O2 2H2O  -  4e-  →  O2  +  4H+	Copper - Cu Cu2+  +  2e-  →  Cu