4.4.3
Electrolysis of Aqueous Solutions & Half Equations
Electrolysis of Aqueous Solutions
Electrolysis of Aqueous Solutions
The products of the electrolysis of aqueous solutions are difficult to predict because the water molecules in the solution split up to give hydrogen (H+) and hydroxide (OH-) ions.
At the anode (positive electrode)
At the anode (positive electrode)
- What is formed at the anode depends on if there are halide ions present:
- If there are halide ions present, the respective halogen forms.
- If there are no halide ions, oxygen forms.
At the cathode (negative electrode)
At the cathode (negative electrode)
- What is formed at the cathode depends on the reactivity of the metal:
- Hydrogen is produced if the metal is higher than hydrogen in the reactivity series.
- The metal is produced if the metal is lower than hydrogen in the reactivity series.
Half Equations
Half Equations
During electrolysis, different reactions take place at the different electrodes. The reactions that happen at each electrode can be shown using half equations. The electrolysis of lead bromide is an example of this:
At the anode (positive electrode)
At the anode (positive electrode)
- Oxidation reactions happen i.e. negatively charged ions lose electrons.
- 2Br- → Br2 + 2e-
At the cathode (negative electrode)
At the cathode (negative electrode)
- Reduction reactions happen i.e. positively charged ions gain electrons.
- Pb2+ + 2e- → Pb
1Atomic Structure
1.1Atoms & Elements
1.1.1Elements & Compounds
1.1.2Chemical Reactions & Equations
1.1.3Mixtures
1.1.4Separating Mixtures
1.1.5Model of the Atom
1.1.6Atom Size & Number
1.1.7Atomic Number - Calculations
1.1.8Isotopes
1.1.9Isotopes HyperLearning
1.1.10Isotopes - Calculations
1.1.11Relative Atomic Mass
1.1.12Electron Structure
1.1.13Periodic Table
1.1.14Metals & Non-Metals
1.1.15Noble Gases
1.1.16Halogens
1.1.17Alkali Metals
1.1.18Transition Metals
1.1.19End of Topic Test - Atomic Structure
1.1.20Grade 9 - Atoms & Elements
1.1.21Exam-Style Questions - Atomic Structure
1.1.22Application Questions - Atomic Structure
2Chemical Bonding
2.1Chemical Bonds
2.2States of Matter
2.3Chemical Properties
2.3.1Chemical Properties of Ionic Compounds
2.3.2Chemical Properties of Small Molecules
2.3.3Molecular Forces & Polymers
2.3.4Metals & Giant Covalent Structures
2.3.5Alloys & Conductors
2.3.6Carbon Structures - Diamond & Graphite
2.3.7Carbon Structures - Graphene & Fullerenes
2.3.8Carbon Structures - Summary
2.3.9Nanoparticles
2.3.10Nanotechnology
2.3.11Surface Area to Volume Ratio & Nanotechnology Uses
2.3.12End of Topic Test - Chemical Bonding
2.3.13Grade 9 - Bonding & Structure
2.3.14Exam-Style Questions - Allotropes of Carbon
3Quantitative Chemistry
3.1Chemical Measurements
3.1.1Conservation of Mass
3.1.2Relative Formula Mass
3.1.3Relative Formula Mass - Calculations
3.1.4Measuring Mass
3.1.5Equations & Formula
3.1.6Moles 1
3.1.7Moles 2
3.1.8Moles 3
3.1.9Moles - Calculations
3.1.10Percentage Yield
3.1.11Percentage Yield - Calculations
3.1.12Moles & Yield
3.1.13Atom Economy
3.1.14Atom Economy - Calculations
3.1.15Concentrations & Amounts
3.1.16Amount of Substance in Relation to Volumes and Gas
3.1.17Concentrations & Amounts - Calculations
3.1.18Empirical Formula - Calculations
3.1.19End of Topic Test - Quant Chemistry
3.1.20Grade 9 - Quantitative Chemistry
3.1.21Exam-Style Questions - Moles
4Chemical Changes
4.1Acids, Alkalis & Redox Reactions
4.2Reactivity of Metals
4.3Reactions of Acids
5Energy Changes
5.1Exothermic & Endothermic Reactions
6The Rate & Extent of Chemical Change
6.1Rate of Reaction
7Organic Chemistry
7.1Carbon Compounds
7.2Alkenes & Alcohols
7.2.1Structure of Alkenes
7.2.2Reactions of Alkenes
7.2.3End of Topic Test - Alkanes & Alkenes
7.2.4Alcohols
7.2.5Reactions of Alcohols
7.2.6Carboxylic Acids
7.2.7Reactions of Carboxylic Acids
7.2.8Addition Polymers
7.2.9Condensation Polymers
7.2.10Naturally Occurring Polymers - Proteins
7.2.11Naturally Occurring Polymers - DNA & Sugars
7.2.12End of Topic Test - Alcohols, Acids & Polymers
7.2.13Grade 9 - Organic Chemistry
7.2.14Exam-Style Questions - Alcohols
8Chemical Analysis
8.1Purity, Formulations & Chromatography
8.2Identification of Common Gases
8.3Identifying Ions
8.3.1Flame Tests
8.3.2Required Practical: Flame Tests
8.3.3Metal Hydroxides
8.3.4Carbonates
8.3.5Halides, Sulfates
8.3.6Methodology for Chemical Analysis
8.3.7Flame Emission Spectroscopy
8.3.8End of Topic Test - Chemical Analysis
8.3.9Grade 9 - Chemical Analysis
8.3.10Exam-Style Questions - Identification of ions
9Chemistry of the Atmosphere
9.1The Earth's Atmosphere
9.1.1Proportions of Gases in the Atmosphere
9.1.2Oxygen & Carbon Dioxide in the Atmosphere
9.1.3Greenhouse Gases & Human Activities
9.1.4Greenhouse Gases & Human Activities
9.1.5Greenhouse Gases & Climate Change
9.1.6Carbon Footprints
9.1.7Common Atmospheric Pollutants & Their Properties
9.1.8End of Topic Test - The Earth
9.1.9Grade 9 - Chemistry of the Atmosphere
9.1.10Exam-Style Questions - Earth's Atmosphere
10Using Resources
10.1Using the Earth's Resources
10.2Life Cycle Assessments & Recycling
10.3Using Materials
10.4The Haber Process & NPK Fertilisers
Jump to other topics
1Atomic Structure
1.1Atoms & Elements
1.1.1Elements & Compounds
1.1.2Chemical Reactions & Equations
1.1.3Mixtures
1.1.4Separating Mixtures
1.1.5Model of the Atom
1.1.6Atom Size & Number
1.1.7Atomic Number - Calculations
1.1.8Isotopes
1.1.9Isotopes HyperLearning
1.1.10Isotopes - Calculations
1.1.11Relative Atomic Mass
1.1.12Electron Structure
1.1.13Periodic Table
1.1.14Metals & Non-Metals
1.1.15Noble Gases
1.1.16Halogens
1.1.17Alkali Metals
1.1.18Transition Metals
1.1.19End of Topic Test - Atomic Structure
1.1.20Grade 9 - Atoms & Elements
1.1.21Exam-Style Questions - Atomic Structure
1.1.22Application Questions - Atomic Structure
2Chemical Bonding
2.1Chemical Bonds
2.2States of Matter
2.3Chemical Properties
2.3.1Chemical Properties of Ionic Compounds
2.3.2Chemical Properties of Small Molecules
2.3.3Molecular Forces & Polymers
2.3.4Metals & Giant Covalent Structures
2.3.5Alloys & Conductors
2.3.6Carbon Structures - Diamond & Graphite
2.3.7Carbon Structures - Graphene & Fullerenes
2.3.8Carbon Structures - Summary
2.3.9Nanoparticles
2.3.10Nanotechnology
2.3.11Surface Area to Volume Ratio & Nanotechnology Uses
2.3.12End of Topic Test - Chemical Bonding
2.3.13Grade 9 - Bonding & Structure
2.3.14Exam-Style Questions - Allotropes of Carbon
3Quantitative Chemistry
3.1Chemical Measurements
3.1.1Conservation of Mass
3.1.2Relative Formula Mass
3.1.3Relative Formula Mass - Calculations
3.1.4Measuring Mass
3.1.5Equations & Formula
3.1.6Moles 1
3.1.7Moles 2
3.1.8Moles 3
3.1.9Moles - Calculations
3.1.10Percentage Yield
3.1.11Percentage Yield - Calculations
3.1.12Moles & Yield
3.1.13Atom Economy
3.1.14Atom Economy - Calculations
3.1.15Concentrations & Amounts
3.1.16Amount of Substance in Relation to Volumes and Gas
3.1.17Concentrations & Amounts - Calculations
3.1.18Empirical Formula - Calculations
3.1.19End of Topic Test - Quant Chemistry
3.1.20Grade 9 - Quantitative Chemistry
3.1.21Exam-Style Questions - Moles
4Chemical Changes
4.1Acids, Alkalis & Redox Reactions
4.2Reactivity of Metals
4.3Reactions of Acids
5Energy Changes
5.1Exothermic & Endothermic Reactions
6The Rate & Extent of Chemical Change
6.1Rate of Reaction
7Organic Chemistry
7.1Carbon Compounds
7.2Alkenes & Alcohols
7.2.1Structure of Alkenes
7.2.2Reactions of Alkenes
7.2.3End of Topic Test - Alkanes & Alkenes
7.2.4Alcohols
7.2.5Reactions of Alcohols
7.2.6Carboxylic Acids
7.2.7Reactions of Carboxylic Acids
7.2.8Addition Polymers
7.2.9Condensation Polymers
7.2.10Naturally Occurring Polymers - Proteins
7.2.11Naturally Occurring Polymers - DNA & Sugars
7.2.12End of Topic Test - Alcohols, Acids & Polymers
7.2.13Grade 9 - Organic Chemistry
7.2.14Exam-Style Questions - Alcohols
8Chemical Analysis
8.1Purity, Formulations & Chromatography
8.2Identification of Common Gases
8.3Identifying Ions
8.3.1Flame Tests
8.3.2Required Practical: Flame Tests
8.3.3Metal Hydroxides
8.3.4Carbonates
8.3.5Halides, Sulfates
8.3.6Methodology for Chemical Analysis
8.3.7Flame Emission Spectroscopy
8.3.8End of Topic Test - Chemical Analysis
8.3.9Grade 9 - Chemical Analysis
8.3.10Exam-Style Questions - Identification of ions
9Chemistry of the Atmosphere
9.1The Earth's Atmosphere
9.1.1Proportions of Gases in the Atmosphere
9.1.2Oxygen & Carbon Dioxide in the Atmosphere
9.1.3Greenhouse Gases & Human Activities
9.1.4Greenhouse Gases & Human Activities
9.1.5Greenhouse Gases & Climate Change
9.1.6Carbon Footprints
9.1.7Common Atmospheric Pollutants & Their Properties
9.1.8End of Topic Test - The Earth
9.1.9Grade 9 - Chemistry of the Atmosphere
9.1.10Exam-Style Questions - Earth's Atmosphere
10Using Resources
10.1Using the Earth's Resources
10.2Life Cycle Assessments & Recycling
10.3Using Materials
10.4The Haber Process & NPK Fertilisers
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