Revision NotesExam QuestionsPast Papers
A LevelChemistryAQARevision NotesOrganic ChemistryIntroduction to Organic ChemistryTypes of Formulae

Types of Formulae (AQA A Level Chemistry): Revision Note

Exam code: 7405

Stewart Hird

Last updated

Types of Formulae

  • The general formula is a formula that represents a homologous series of compounds using letters and numbers

    • Eg. the general formula of alkanes is CnH2n+2

    • A homologous series is a group of organic compounds that have the same functional group, the same general formula and the same chemical properties

  • The structural formula is a formula that shows how the atoms are bonded to each carbon atom in a molecule

  • The displayed formula is a 2D representation of an organic molecule showing all its atoms (by their symbols) and their bonds (by single, double or triple bonds)

  • The skeletal formula is a simplified displayed formula with all the carbon and hydrogen (C-H) bonds removed

Overview of the Formulae of Organic Compounds Table

 

Worked Example

Drawing skeletal formulae of molecules

Draw the skeletal formula of the following molecules:

  1. CH3(CH2)3OH

  2. (CH3)2CHCH2OH

  3. CH3CH2OCH2CH3

Answer:

An Introduction to AS Level Organic Chemistry Answer Worked example - Drawing skeletal formulae of molecules, downloadable AS & A Level Chemistry revision notes

Worked Example

Drawing displayed formulae of molecules

Draw the displayed formula of the following molecules: 

  1. CH2CHCH3

  2. CH2CHCH2COOH

  3. CH2ClCH2COOCH3

Answer:

An Introduction to AS Level Organic Chemistry Answer Worked example - Drawing displayed formulae of molecules, downloadable AS & A Level Chemistry revision notes

Molecular & Empirical Formulae

  • The molecular formula shows the number and type of each atom in a molecule

    • Eg. the molecular formula of ethanoic acid is C2H4O2

  • The empirical formula shows the simplest whole number ratio of the elements present in one molecule of the compound

    • Eg. the empirical formula of ethanoic acid is CH2O

Worked Example

Deducing molecular & empirical formulae Deduce the molecular and empirical formula of the following compounds: 

Answer

3-1-an-introduction-to-as-level-organic-chemistry-answers-worked-example---deducing-molecular-and-empirical-formulae_2


You've read 0 of your 5 free revision notes this week

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

    Test yourself

    Did this page help you?

    Previous:Functional GroupsNext:Nomenclature
    Stewart Hird

    Author: Stewart Hird

    Expertise: Chemistry Content Creator

    Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.