Required Practical: Electrolysis

Electrolysis of Aqueous Solutions Using Inert Electrodes

This experiment investigates which ions are discharged during the electrolysis of aqueous ionic solutions using inert electrodes, and identifies the products formed at each electrode.

Apparatus and materials

DC power supply
Two inert electrodes (carbon or platinum)
Beaker
Test tubes or gas collection tubes
Retort stand and clamps
Leads and crocodile clips
Range of aqueous solutions (such as copper(II) sulfate, copper(II) chloride, sodium chloride, sodium nitrate, sodium bromide)
Splints and litmus paper for gas testing

Method

Assemble the electrolysis apparatus:
- Connect the electrodes to the DC power pack, ensuring one electrode is attached to each terminal.
Pour an aqueous solution into the beaker so that both electrodes are submerged.
Switch on the power supply and allow electrolysis to happen for several minutes.
Observe any visible changes, such as gas bubbles or metal deposition on the electrodes.

Method (continuation)

Collect any gases formed using inverted test tubes.
Test the gases using the following standard gas tests:
- Hydrogen: a lighted splint produces a squeaky pop
- Oxygen: a glowing splint relights
- Chlorine: damp blue litmus paper turns red, then bleaches white
Record all observations, including the identity of gases and any metal deposits.
Repeat for at least five different electrolyte solutions.

Variables

Independent variable:
- Type of aqueous solution used (e.g., copper sulfate, sodium chloride)
Dependent variable:
- Products formed at each electrode
Control variables:
- Current supplied, size and type of electrodes, volume and concentration of solution, and duration of electrolysis

Hazards and safety precautions

Copper(II) compounds:
- Harmful if ingested; avoid contact with skin.
Chlorine gas:
- Toxic; carry out experiments in a well-ventilated room or fume cupboard.
Electric current:
- Avoid contact with solutions while the circuit is live.
Always wear safety goggles and a lab coat, and wash hands after handling chemicals.

Analysing the results

After electrolysis, identify which products appeared at the anode and cathode for each solution. Compare the outcomes with your original hypothesis.
Typical observations might include:
- Copper(II) sulfate: copper metal at the cathode; oxygen at the anode.
- Sodium chloride: hydrogen at the cathode; chlorine at the anode.

1Atomic Structure

1.1Atoms & Elements

1.1.1Elements & Compounds

1.1.2Chemical Formula

1.1.3Chemical Reactions

1.1.4Chemical Equations

1.1.5Mixtures

1.1.6Separating Mixtures

1.1.7Separating Mixtures 2

1.1.8Model of the Atom

1.1.9Sub-Atomic Particles

1.1.10Atom Size

1.1.11Atomic Number

1.1.12Atomic Number - Calculations

1.1.13Isotopes

1.1.14Isotopes HyperLearning

1.1.15Isotopes - Calculations

1.1.16Relative Atomic Mass

1.1.17Electron Structure

1.1.18Periodic Table

1.1.19The History of the Periodic Table

1.1.20Metals & Non-Metals

1.1.21Noble Gases

1.1.22Displacement Reaction

1.1.23Halogens

1.1.24Alkali Metals

1.1.25Alkali Metals - Properties

1.1.26Transition Metals

1.1.27Transition Metals - Special Properties

1.1.28End of Topic Test - Atomic Structure

1.1.29Grade 9 - Atoms & Elements

1.1.30Exam-Style Questions - Atomic Structure

1.1.31Application Questions - Atomic Structure

1.1.32Diagnostic Misconceptions - Balancing Equations

1.1.33Diagnostic Misconceptions - Isotopes

2Chemical Bonding

2.1Chemical Bonds

2.1.1Types of Bonds

2.1.2Ions

2.1.3Ionic Bonds

2.1.4Ionic Compounds

2.1.5Empirical Formulae

2.1.6Covalent Bonds

2.1.7Metallic Bonds

2.1.8Covalent Bond Examples

2.1.9Representing Covalent Bonds

2.1.10Dots-And-Cross Diagrams

2.1.11Dots-And-Cross Diagrams 2

2.1.12Exam-Style Questions - Chemical Bonds

2.2States of Matter

2.2.1States of Matter

2.2.2Simple Sphere

2.2.3Changing State

2.2.4Changing State 2

2.2.5Changing State HyperLearning

2.2.6State Symbols

2.2.7Exam-Style Questions - States of Matter

2.2.8Diagnostic Misconceptions - Particles

2.3Chemical Properties

2.3.1Ionic Compounds

2.3.2Chemical Properties of Ionic Compounds

2.3.3Small Molecules

2.3.4Chemical Properties of Small Molecules

2.3.5Molecular Forces - Polymers

2.3.6Molecular Forces - Polypropene

2.3.7Giant Covalent Structures

2.3.8Metals

2.3.9Alloys

2.3.10Conductors

2.3.11Carbon Structures - Diamond

2.3.12Carbon Structures - Graphite

2.3.13Carbon Structures - Graphene

2.3.14Carbon Structures - Fullerenes

2.3.15Carbon Structures - Summary

2.3.16Clumps

2.3.17Nanoparticles

2.3.18Nanotechnology

2.3.19Nanotechnology 2

2.3.20Surface Area to Volume Ratio

2.3.21Nanotechnology Uses

2.3.22End of Topic Test - Chemical Bonding

2.3.23Grade 9 - Bonding & Structure

2.3.24Exam-Style Questions - Allotropes of Carbon

2.3.25Diagnostic Misconceptions - Conducting Electricity

2.3.26Diagnostic Misconceptions - Small Molecules

2.3.27Diagnostic Misconceptions - Drawing Polymers

3Quantitative Chemistry

3.1Chemical Measurements

3.1.1Conservation of Mass

3.1.2Relative Formula Mass

3.1.3Calculating Relative Formula Mass

3.1.4Relative Formula Mass - Calculations

3.1.5Changing Mass

3.1.6Measuring Mass

3.1.7Equations

3.1.8Empirical Formula

3.1.9Introducing Moles

3.1.10Relative Formula Mass

3.1.11Amounts of Substance

3.1.12Moles to Balance Equations

3.1.13Limiting Reactants

3.1.14Concentration of Solutions

3.1.15Moles - Calculations

3.1.16Percentage Yield

3.1.17Calculating Yield

3.1.18Percentage Yield - Calculations

3.1.19Moles & Yield

3.1.20Moles & Yield 2

3.1.21Atom Economy

3.1.22Reaction Pathway

3.1.23Atom Economy - Calculations

3.1.24Concentrations of Solute

3.1.25Calculating the Amount of Solute

3.1.26Amount of Substance in Relation to Volumes and Gas

3.1.27Concentrations & Amounts - Calculations

3.1.28Empirical Formula - Calculations

3.1.29End of Topic Test - Quant Chemistry

3.1.30Grade 9 - Quantitative Chemistry

3.1.31Exam-Style Questions - Moles

3.1.32Diagnostic Misconceptions - Calculating RFM

3.1.33Diagnostic Misconceptions - Moles

4Chemical Changes

4.1Acids, Alkalis & Redox Reactions

4.1.1Acids & Alkalis

4.1.2Redox Reactions - Oxidation

4.1.3Redox Reactions - Metal Oxide

4.2Reactivity of Metals

4.2.1Reactivity Diagram

4.2.2Displacement Reactions

4.2.3Displacement Reactions - Halogens

4.2.4Reactions with Water

4.2.5Reactions with Acid

4.2.6Reactivity Tests

4.2.7Reactivity Tests 2

4.2.8Extraction of Metals

4.2.9Exam-Style Questions - Displacement Reactions

4.3Reactions of Acids

4.3.1Reactions of Metals with Acids

4.3.2Redox Reactions

4.3.3Neutralisation of Acids

4.3.4Soluble Salts

4.3.5Required Practical: Separating Mixtures

4.3.6The pH Scale

4.3.7Numerical pH Scale

4.3.8Measuring pH

4.3.9Neutralisation & Titrations

4.3.10Neutralisation & Titrations 2

4.3.11Neutralisation & Titrations 3

4.3.12Neutralisation & Titrations 4

4.3.13Strong and Weak Acids

4.3.14Required Practical: Titration

4.4Electrolysis

4.4.1Electrolysis Process

4.4.2Molten Ionic Compound

4.4.3Metal Extraction

4.4.4Electrolysis of Aqueous Solutions

4.4.5Required Practical: Electrolysis

4.4.6Half Equations

4.4.7End of Topic Test - Chemical Changes

4.4.8Grade 9 - Chemical Changes

4.4.9Exam-Style Questions - Electrolysis

5Energy Changes

5.1Exothermic & Endothermic Reactions

5.1.1Energy Conservation

5.1.2Exothermic Reactions

5.1.3Endothermic Reactions

5.1.4Required Practical: Temperature Changes

5.1.5Reaction Profiles Requirements

5.1.6Reaction Profiles

5.1.7Reaction Profiles - Catalysed vs Uncatalysed

5.1.8Reaction Profiles - Chemical Bonds

5.1.9Diagnostic Misconceptions - Source of Energy

5.2Chemical Cells & Fuel Cells

5.2.1Chemical Cells

5.2.2Changing Voltage Output

5.2.3Batteries

5.2.4Charging of Cells

5.2.5Fuel Cells

5.2.6Hydrogen Fuel Cell

5.2.7Hydrogen as an Alternative

5.2.8End of Topic Test - Energy Changes

5.2.9Grade 9 - Energy Changes

5.2.10Exam-Style Questions - Fuel Cells

6The Rate & Extent of Chemical Change

7Organic Chemistry

7.1Carbon Compounds

7.1.1Crude Oil

7.1.2Properties of Hydrocarbons

7.1.3Alkanes

7.1.4Smallest Alkanes

7.1.5Fractional Distillation

7.1.6Process of Fractional Distillation

7.1.7Homologous Series

7.1.8Burning Hydrocarbons

7.1.9Heavy Fractions of Crude Oil

7.1.10Cracking

7.1.11Uses of Alkenes

7.1.12Exam-Style Questions - Organic Compounds

7.2Alkenes & Alcohols

8Chemical Analysis

9Chemistry of the Atmosphere

9.1The Earth's Atmosphere

9.1.1Proportions of Gases in the Atmosphere

9.1.2The Earth's Early Atmosphere

9.1.3Oxygen in the Atmosphere

9.1.4Carbon Dioxide in the Atmosphere

9.1.5Greenhouse Gases

9.1.6Greenhouse Gases & Human Activities

9.1.7Greenhouse Gases & Climate

9.1.8Climate Change

9.1.9Carbon Footprints

9.1.10Carbon Footprints Barriers

9.1.11Common Atmospheric Pollutants

9.1.12Properties of Atmospheric Pollutants

9.1.13End of Topic Test - The Earth

9.1.14Grade 9 - Chemistry of the Atmosphere

9.1.15Exam-Style Questions - Earth's Atmosphere

9.1.16Diagnostic Misconceptions - Greenhouse Effect

10Using Resources

10.1Using the Earth's Resources

10.1.1Potable Water

10.1.2Potable Water Sources

10.1.3Potable Water in the UK

10.1.4Potable Water in Saudi Arabia

10.1.5Required Practical: Analysing and Purifying Water

10.1.6Natural Resources

10.1.7Uses of Natural Resources

10.1.8Waste Water

10.1.9Sewage Treatment

10.1.10Metal Ore Extraction

10.1.11Properties of Copper

10.1.12Overexploitation of Extraction Methods

10.1.13Alternative Extraction Methods

10.2Life Cycle Assessments & Recycling

10.2.1Life Cycle Assessments

10.2.2Comparative Life Cycle Assessments

10.2.3Difficulties with LCA

10.2.4Reducing Resource Usage

10.2.5Reducing Use of Glass

10.2.6Reducing Use of Metal

10.2.7Exam-Style Questions - Life Cycle Assessments

10.3Using Materials

10.3.1Corrosion

10.3.2Preventing Corrosion

10.3.3Alloys

10.3.4Ceramics

10.3.5Polymers

10.3.6Composites

10.4The Haber Process & NPK Fertilisers

10.4.1Plants and Nitrogen

10.4.2The Haber Process

10.4.3The Haber Process - Equation

10.4.4The Haber Process - Trade-Offs

10.4.5Importance of Fertilisers

10.4.6Formulated vs Manure Fertilisers

10.4.7NPK Fertilisers - N-containing Compound

10.4.8NPK Fertilisers - P-containing Compound

10.4.9NPK Fertilisers - K-containing Compound

10.4.10Nitrogen, Phosphorus and Potassium

10.4.11End of Topic Test - Resources

10.4.12Grade 9 - Using Resources

10.4.13Exam-Style Questions - The Haber Process

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