2.1.5

Empirical Formulae

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Empirical Formulae

You can work out the proportion of each ion in a compound. The empirical formula of an ionic compound is the simplest ratio of ions possible.

Ca<sup>2+</sup> and F<sup>-</sup>

Ca2+ and F-

  • In order for the charges to balance out and for the overall formula to be neutral, there must be 2 F- ions for each Ca2+ ion.
    • The empirical formula is CaF2
Na<sup>+</sup> + SO<sub>4</sub><sup>2-</sup>

Na+ + SO42-

  • In order for the charges to balance out and for the overall formula to be neutral, there must be 2 Na+ ions for each SO42- ion.
    • The empirical formula is Na2SO4.
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1

Atomic Structure

1.1

Atoms & Elements

1.1.1Elements & Compounds1.1.2Chemical Formula1.1.3Chemical Reactions1.1.4Chemical Equations1.1.5Mixtures1.1.6Separating Mixtures1.1.7Separating Mixtures 21.1.8Model of the Atom1.1.9Sub-Atomic Particles1.1.10Atom Size1.1.11Atomic Number1.1.12Atomic Number - Calculations1.1.13Isotopes1.1.14Isotopes HyperLearning1.1.15Isotopes - Calculations1.1.16Relative Atomic Mass1.1.17Electron Structure1.1.18Periodic Table1.1.19The History of the Periodic Table1.1.20Metals & Non-Metals1.1.21Noble Gases1.1.22Displacement Reaction1.1.23Halogens1.1.24Alkali Metals1.1.25Alkali Metals - Properties1.1.26Transition Metals1.1.27Transition Metals - Special Properties1.1.28End of Topic Test - Atomic Structure1.1.29Grade 9 - Atoms & Elements1.1.30Exam-Style Questions - Atomic Structure1.1.31Application Questions - Atomic Structure1.1.32Diagnostic Misconceptions - Balancing Equations1.1.33Diagnostic Misconceptions - Isotopes
2

Chemical Bonding

2.1

Chemical Bonds

2.1.1Types of Bonds2.1.2Ions2.1.3Ionic Bonds2.1.4Ionic Compounds2.1.5Empirical Formulae2.1.6Covalent Bonds2.1.7Metallic Bonds2.1.8Covalent Bond Examples2.1.9Representing Covalent Bonds2.1.10Dots-And-Cross Diagrams2.1.11Dots-And-Cross Diagrams 22.1.12Exam-Style Questions - Chemical Bonds
2.2

States of Matter

2.2.1States of Matter2.2.2Simple Sphere2.2.3Changing State2.2.4Changing State 22.2.5Changing State HyperLearning2.2.6State Symbols2.2.7Exam-Style Questions - States of Matter2.2.8Diagnostic Misconceptions - Particles
2.3

Chemical Properties

2.3.1Ionic Compounds2.3.2Chemical Properties of Ionic Compounds2.3.3Small Molecules2.3.4Chemical Properties of Small Molecules2.3.5Molecular Forces - Polymers2.3.6Molecular Forces - Polypropene2.3.7Giant Covalent Structures2.3.8Metals2.3.9Alloys2.3.10Conductors2.3.11Carbon Structures - Diamond2.3.12Carbon Structures - Graphite2.3.13Carbon Structures - Graphene2.3.14Carbon Structures - Fullerenes2.3.15Carbon Structures - Summary2.3.16Clumps2.3.17Nanoparticles2.3.18Nanotechnology2.3.19Nanotechnology 22.3.20Surface Area to Volume Ratio2.3.21Nanotechnology Uses2.3.22End of Topic Test - Chemical Bonding2.3.23Grade 9 - Bonding & Structure2.3.24Exam-Style Questions - Allotropes of Carbon2.3.25Diagnostic Misconceptions - Conducting Electricity2.3.26Diagnostic Misconceptions - Small Molecules2.3.27Diagnostic Misconceptions - Drawing Polymers
3

Quantitative Chemistry

3.1

Chemical Measurements

3.1.1Conservation of Mass3.1.2Relative Formula Mass3.1.3Calculating Relative Formula Mass3.1.4Relative Formula Mass - Calculations3.1.5Changing Mass3.1.6Measuring Mass3.1.7Equations3.1.8Empirical Formula3.1.9Introducing Moles3.1.10Relative Formula Mass3.1.11Amounts of Substance3.1.12Moles to Balance Equations3.1.13Limiting Reactants3.1.14Concentration of Solutions3.1.15Moles - Calculations3.1.16Percentage Yield3.1.17Calculating Yield3.1.18Percentage Yield - Calculations3.1.19Moles & Yield3.1.20Moles & Yield 23.1.21Atom Economy3.1.22Reaction Pathway3.1.23Atom Economy - Calculations3.1.24Concentrations of Solute3.1.25Calculating the Amount of Solute3.1.26Amount of Substance in Relation to Volumes and Gas3.1.27Concentrations & Amounts - Calculations3.1.28Empirical Formula - Calculations3.1.29End of Topic Test - Quant Chemistry3.1.30Grade 9 - Quantitative Chemistry3.1.31Exam-Style Questions - Moles3.1.32Diagnostic Misconceptions - Calculating RFM3.1.33Diagnostic Misconceptions - Moles
4

Chemical Changes

4.1

Acids, Alkalis & Redox Reactions

4.1.1Acids & Alkalis4.1.2Redox Reactions - Oxidation4.1.3Redox Reactions - Metal Oxide
4.2

Reactivity of Metals

4.2.1Reactivity Diagram4.2.2Displacement Reactions4.2.3Displacement Reactions - Halogens4.2.4Reactions with Water4.2.5Reactions with Acid4.2.6Reactivity Tests4.2.7Reactivity Tests 24.2.8Extraction of Metals4.2.9Exam-Style Questions - Displacement Reactions
4.3

Reactions of Acids

4.3.1Reactions of Metals with Acids4.3.2Redox Reactions4.3.3Neutralisation of Acids4.3.4Soluble Salts4.3.5Required Practical: Separating Mixtures4.3.6The pH Scale4.3.7Numerical pH Scale4.3.8Measuring pH4.3.9Neutralisation & Titrations4.3.10Neutralisation & Titrations 24.3.11Neutralisation & Titrations 34.3.12Neutralisation & Titrations 44.3.13Strong and Weak Acids4.3.14Required Practical: Titration
4.4

Electrolysis

4.4.1Electrolysis Process4.4.2Molten Ionic Compound4.4.3Metal Extraction4.4.4Electrolysis of Aqueous Solutions4.4.5Required Practical: Electrolysis4.4.6Half Equations4.4.7End of Topic Test - Chemical Changes4.4.8Grade 9 - Chemical Changes4.4.9Exam-Style Questions - Electrolysis
5

Energy Changes

5.1

Exothermic & Endothermic Reactions

5.1.1Energy Conservation5.1.2Exothermic Reactions5.1.3Endothermic Reactions5.1.4Required Practical: Temperature Changes5.1.5Reaction Profiles Requirements5.1.6Reaction Profiles5.1.7Reaction Profiles - Catalysed vs Uncatalysed5.1.8Reaction Profiles - Chemical Bonds5.1.9Diagnostic Misconceptions - Source of Energy
5.2

Chemical Cells & Fuel Cells

5.2.1Chemical Cells5.2.2Changing Voltage Output5.2.3Batteries5.2.4Charging of Cells5.2.5Fuel Cells5.2.6Hydrogen Fuel Cell5.2.7Hydrogen as an Alternative5.2.8End of Topic Test - Energy Changes5.2.9Grade 9 - Energy Changes5.2.10Exam-Style Questions - Fuel Cells
6

The Rate & Extent of Chemical Change

6.1

Rate of Reaction

6.1.1Chemical Reactions6.1.2Plotting Reaction Rates6.1.3Required Practical: Effect of Concentration6.1.4Collision Theory6.1.5Key Factors of Rate of Reaction6.1.6Catalysts6.1.7Catalysts in Industry
6.2

Reversible Reactions

6.2.1Reversible Reactions6.2.2Dynamic Equilibrium6.2.3Conditions and Equilibrium6.2.4Equilibrium Position - Temperature6.2.5Equilibrium Position - Pressure6.2.6Equilibrium Position - Concentration6.2.7End of Topic Test - Rates of Reaction6.2.8Grade 9 - Rate & Extent of Chemical Change6.2.9Exam-Style Questions - Reversible Reactions6.2.10Diagnostic Misconceptions - Temperature6.2.11Diagnostic Misconceptions - Pressure6.2.12Diagnostic Misconceptions - Concentration6.2.13Diagnostic Misconceptions - Catalysts
7

Organic Chemistry

7.1

Carbon Compounds

7.1.1Crude Oil7.1.2Properties of Hydrocarbons7.1.3Alkanes7.1.4Smallest Alkanes7.1.5Fractional Distillation7.1.6Process of Fractional Distillation7.1.7Homologous Series7.1.8Burning Hydrocarbons7.1.9Heavy Fractions of Crude Oil7.1.10Cracking7.1.11Uses of Alkenes7.1.12Exam-Style Questions - Organic Compounds
7.2

Alkenes & Alcohols

7.2.1Structure of Alkenes7.2.2The Shortest Alkenes7.2.3Reactions of Alkenes7.2.4Types of Alkene Reactions7.2.5Alcohols7.2.6The Smallest Alcohols7.2.7Reactions of Alcohols7.2.8Fermentation7.2.9Carboxylic Acids7.2.10The Smallest Carboxylic Acids7.2.11Reactions of Carboxylic Acids7.2.12Addition Polymers7.2.13Addition Polymers Examples7.2.14Condensation Polymers7.2.15Amino Acids7.2.16Naturally Occurring Polymers - Protein (Formation)7.2.17Naturally Occurring Polymers - Protein (Roles)7.2.18Naturally Occurring Polymers - DNA7.2.19Naturally Occurring Polymers - Others7.2.20End of Topic Test - Alkanes & Alkenes7.2.21End of Topic Test - Alcohols, Acids & Polymers7.2.22Grade 9 - Organic Chemistry7.2.23Exam-Style Questions - Alcohols
8

Chemical Analysis

8.1

Purity, Formulations & Chromatography

8.1.1Purity8.1.2Formulations8.1.3Chromatography8.1.4Paper Chromatography 18.1.5Paper Chromatography 28.1.6Required Practical - Paper Chromatography8.1.7Diagnostic Misconceptions - Purity
8.2

Identification of Common Gases

8.2.1Identification of Hydrogen8.2.2Identification of Oxygen8.2.3Identification of Carbon Dioxide8.2.4Identification of Chlorine
8.3

Identifying Ions

8.3.1Flame Tests8.3.2Required Practical: Flame Tests8.3.3Metal Hydroxides8.3.4Metal Hydroxides 28.3.5Carbonates8.3.6Halides8.3.7Sulfates8.3.8Methodology for Chemical Analysis8.3.9Methodology for Chemical Analysis 28.3.10Flame Emission Spectroscopy8.3.11Flame Emission Spectroscopy Analysis8.3.12End of Topic Test - Chemical Analysis8.3.13Grade 9 - Chemical Analysis8.3.14Exam-Style Questions - Identification of ions
9

Chemistry of the Atmosphere

9.1

The Earth's Atmosphere

9.1.1Proportions of Gases in the Atmosphere9.1.2The Earth's Early Atmosphere9.1.3Oxygen in the Atmosphere9.1.4Carbon Dioxide in the Atmosphere9.1.5Greenhouse Gases9.1.6Greenhouse Gases & Human Activities9.1.7Greenhouse Gases & Climate9.1.8Climate Change9.1.9Carbon Footprints9.1.10Carbon Footprints Barriers9.1.11Common Atmospheric Pollutants9.1.12Properties of Atmospheric Pollutants9.1.13End of Topic Test - The Earth9.1.14Grade 9 - Chemistry of the Atmosphere9.1.15Exam-Style Questions - Earth's Atmosphere9.1.16Diagnostic Misconceptions - Greenhouse Effect
10

Using Resources

10.1

Using the Earth's Resources

10.1.1Potable Water10.1.2Potable Water Sources10.1.3Potable Water in the UK10.1.4Potable Water in Saudi Arabia10.1.5Required Practical: Analysing and Purifying Water10.1.6Natural Resources10.1.7Uses of Natural Resources10.1.8Waste Water10.1.9Sewage Treatment10.1.10Metal Ore Extraction10.1.11Properties of Copper10.1.12Overexploitation of Extraction Methods10.1.13Alternative Extraction Methods
10.2

Life Cycle Assessments & Recycling

10.2.1Life Cycle Assessments10.2.2Comparative Life Cycle Assessments10.2.3Difficulties with LCA10.2.4Reducing Resource Usage10.2.5Reducing Use of Glass10.2.6Reducing Use of Metal10.2.7Exam-Style Questions - Life Cycle Assessments
10.3

Using Materials

10.3.1Corrosion10.3.2Preventing Corrosion10.3.3Alloys10.3.4Ceramics10.3.5Polymers10.3.6Composites
10.4

The Haber Process & NPK Fertilisers

10.4.1Plants and Nitrogen10.4.2The Haber Process10.4.3The Haber Process - Equation10.4.4The Haber Process - Trade-Offs10.4.5Importance of Fertilisers10.4.6Formulated vs Manure Fertilisers10.4.7NPK Fertilisers - N-containing Compound10.4.8NPK Fertilisers - P-containing Compound10.4.9NPK Fertilisers - K-containing Compound10.4.10Nitrogen, Phosphorus and Potassium10.4.11End of Topic Test - Resources10.4.12Grade 9 - Using Resources10.4.13Exam-Style Questions - The Haber Process

Practice questions on Empirical Formulae

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    If an ionic compound contained Mg<sup>2+</sup> and O<sup>2-</sup> ions, what would the empirical formula be?Multiple choice
  2. 2
    What is the empirical formula of sodium oxide?Flashcard
  3. 3
    Which of the following is the correct empirical formula?True / false
  4. 4
    Explain why ionic compounds are largely soluble in waterMultiple choice
  5. 5
    Explain why ionic compounds conduct electricityMultiple choice
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Ionic Compounds

Covalent Bonds